CAMBRIDGE, MASS. -- Robert Pirsig, author of the most famous book about motorcycles ever, doesn't have a license to drive one. When he resettled near here a couple of years ago, his old permit had expired. Part of the requirement for getting a new one was taking a test.

He flunked.

It could happen to anyone, but one of Pirsig's mistakes was ... unusual. Which hand do you hold out when making a left turn? For some reason he answered the right hand. He's not sure why.

Silly mistake, but somehow it seems fitting. Pirsig just doesn't operate the way most folks do. This guy's on a different wavelength, always has been.

He could have reapplied for the permit, but the more he thought about it the less he wanted to ride his Honda Superhawk. Suppose he had an accident? Then all his efforts toward completing his second book -- a marathon that, in the end, totaled 17 years -- would have been wasted.

It was in the same spirit that, as he was wrapping up work last year, Pirsig disregarded the pain in his side. It turned out to be an infected gallbladder, and he made sure that the last thing he did before going in the hospital was finish the manuscript. If he died on the operating table, at least the book would survive.

For a while, Pirsig even quit talking to people except for his wife, Wendy. Admittedly, he was never very keen on chatting in the best of times. The problem was, when he was done with the conversation -- and it could be about something as simple as the laundry or the weather -- he would find himself thinking about it for the next day or two, turning it over again and again in his mind. It was almost like a form of pollution.

In spite of these precautions, the book didn't come easily. "To get a line that is exactly right, you sometimes have to sacrifice everything," Pirsig believes. "That goes for being a celebrity, for interaction with people, personal comfort, everything. It's that slight difference between a line that's almost right and one that's exactly right."

Although the book is being published this month, he still doesn't want to be a celebrity. He's careful not to specify what state he lives in, although seeing as it's about an hour and a half drive from this hotel room, it seems to be southern New Hampshire. He won't confirm this, doesn't want people somehow dropping by. The thought of meeting his readers in the flesh gives him the willies.

Nothing personal -- he doesn't want to meet anyone. He stopped talking on the telephone while working on the book, and has no inclination to start again.

"You know what writing is like," he says. "You get obsessed."

No one, it seems fair to say, more deeply than he.

If you had to select the best-selling book of serious nonfiction for the past 20 years, "Zen and the Art of Motorcycle Maintenance" would be one of the top contenders. What makes this even more impressive is the totally unexpected way "Zen" arrived: It was an autobiographical work that read like a novel, written by an unpublished former mental patient then living in Minnesota.

At first, no publisher would touch it. A critique of reality through the prism of a motorcycle trip? The premise got 121 rejections before William Morrow took a chance. Pirsig's editor gave him a $3,000 advance and warned he was unlikely to see any more.

Famous last words: Three months after publication in April 1974, "Zen" had sold 50,000 copies and earned $370,000 for the paperback rights. George Steiner, a literary critic who usually doesn't bother to read anything that wasn't first published in German or ancient Greek, compared it favorably to "Moby-Dick." Movie deals were made with a succession of Hollywood figures that culminated with Robert Redford. Total sales are now approaching 4 million copies.

Boil the book down to a sentence and it would be this: To understand the world, to appreciate what is good and true, you don't need anyone or anything else. That sounds mundane enough, but after the excesses of the 1960s it was a truly radical notion. Forget about drugs, sex, revolution, encounter groups, the maharishi, all the other highly touted solutions of the era. They're all external, all useless. Try thinking instead. You don't even need your own motorcycle. "The real cycle you're working on," Pirsig wrote, "is a cycle called 'yourself.' "

"Zen," subtitled "An Inquiry Into Values" and told from the viewpoint of a 1968 motorcycle trip Pirsig took with his 11-year-old son Chris, looks back to the author's years as a teacher at Montana State University. He was then a "fanatic hunter," determined to solve philosophic questions that had never been solved before. It was an exhilarating intellectual adventure, but it ended with a complete breakdown, hospitalization and extensive shock treatment.

The therapy didn't work. During the course of the narrative, as Pirsig tries to tell the reader about his previous existence, his former self, named Phaedrus after a bit player in one of Plato's dialogues, comes back. Slowly Phaedrus takes over the new, adjusted, benign personality, and in the process rescues Chris from his own bout of mental illness. "We've won it," the possibly newly insane narrator insists on the last page. "It's going to get better now. You can sort of tell these things."

The story, although changed a bit for rhetorical purposes, was basically true. The new book, "Lila" -- this time subtitled "An Inquiry Into Morals" -- is more of a mixed bag. There's a boat trip down the Hudson by a character alternately called the Captain or Phaedrus whose background of mental breakdown, best-selling book etc. resembles Pirsig's quite closely.

On the other hand, the woman he picks up in a riverside town, a former prostitute named Lila who is on the way to her own sort of breakdown, is completely fictional. And the philosophical ruminations, which range from how the idea that "all men are created equal" came from the American Indian to the post-World War I shift from social domination of intellect to intellectual domination of society, are meant to be taken very seriously indeed. They're the whole reason the book exists. Lila is there just to liven things up.

"Reading metaphysics is like reading blueprints," Pirsig explains. "There's no way to make it very interesting, and no way you're going to write a bestseller. Metaphysics needs the same kind of background 'Zen' had. I had been sailing at that time, and thought I'd encase it in a river story. Also this is a book about morals, and I wanted a moral situation. So I followed the fiction writer's basic structure of 'Get your hero up a tree, throw rocks at him, and get him down again.' " In a very philosophical manner, that is.

Some of the reviewers, it's easy to predict, are going to throw rocks of their own. "Lila" is not only unconventional, it's tough going in the philosophy sections. You've got to work at sorting it out, and even then it's no sure thing.

"There's an old analogy to a cup of tea," Pirsig warns early in the book. "If you want to drink new tea you have to get rid of the old tea that's in your cup, otherwise your cup just overflows and you get a wet mess. Your head is like that cup. It has a limited capacity and if you want to learn something about the world you should keep your head empty in order to learn it. It's very easy to spend your whole life swishing old tea around in your cup thinking it's great stuff because you've never really tried anything new, because you could never get it in, because the old stuff prevented its entry because you were so sure the old stuff was so good, because you never really tried anything new ... on and on in an endless circular pattern."

This, it should be noted, is one of the simpler passages in "Lila." Perhaps someday Wendy Pirsig will publish a book about her husband that will serve as a gloss on him and his philosophy, make both of them easier to understand. She's certainly taking a lot of notes. "Does it bother you?" she asks from her perch on the bed. It's an old habit: She was a freelance writer when they met in the mid-'70s as he was sailing his 32-foot oceangoing sailboat down the Intra-Coastal Waterway. Pirsig had left Minnesota and his first wife, fleeing the perils of unexpected celebrityhood -- a girl squealing in ecstasy at a speaking engagement, a woman broadcasting executive telling him, "I must have you. I mean you."

In 1979 there came a much more violent break with the past. Chris, who had dodged the threat of mental illness outlined in "Zen" and had become a student at a Zen center in San Francisco, was stabbed to death with a kitchen knife by two men. It was one of those inexplicable, unsolved street crimes that have become a hallmark of our era. "I go on living, more from force of habit than anything else," Pirsig wrote in an autobiographical piece about that period.

Not many months later, Wendy became pregnant. Pirsig was in his early fifties then, and thought he was through with child-rearing. Urged by a force they didn't understand, the couple went ahead and had the child. Their daughter Nell is now 10, and she mended the pattern that Chris's death had broken.

Focusing on work couldn't have hurt either, especially given the enormous amount of concentration Pirsig devotes to the job. He's always been that way. When he started "Zen" he went to bed at 6 p.m., got up at 2 a.m. and wrote until he went to his job as a technical writer at 8 a.m. "Writing is like being a lighthouse keeper," he says. "You've got a job to do. If you say, 'I'll just do it Mondays and Wednesdays,' something's going to go aground."

Back From the Terror The phone rings and Pirsig looks a bit alarmed, the way you or I would be if we heard a noise in the distance that might be a gunshot. Wendy answers. It's the publicist, trying to bring things to a conclusion. Pirsig would rather go on talking. "I have problems meeting people," he says, "but once I get started it's all right."

Neither "Zen" nor "Lila" has the usual author photo on its back cover, perpetuating the notion of a man of mystery. If you saw Pirsig in the supermarket you wouldn't look twice -- unless you got a close look at the eyes. They're sunk way back into his skull, the eyes of someone who has gone over to the other side and come back.

It wasn't a pleasant voyage. For all Pirsig's sympathy with the mentally ill, he never romanticizes madness. He remembers his own experience too well.

Chicago, 1963: Pirsig and the 6-year-old Chris were driving around, looking for the place where they were going to buy some bunk beds. Pirsig, his mind completely detached from his real-life surroundings, couldn't remember where the store was. One gray building resembled the next, one street sign was much like another. They drove on and on, until poor Chris, sensing something was wrong, began to panic.

Pirsig's voice, which normally has a high Midwest twang, gets softer as he talks. "I had forgotten about that incident for years. ... There's a street where we stopped ... and there was a car behind us." His voice is barely audible now. "We must have been there a minute. And nothing happened. It's hard to tell you but there was no force to go forward. The guy behind honked, and then honked again, and finally worked his way around, in that kind of disgusted way of driving. ... It was the first time Chris had ever been able to guess, to feel that something was wrong."

Somehow, Pirsig managed to start driving again. Maybe it was Chris's anxiety. "It was a little like the mental blockage when you're going to give a speech. Suddenly you don't know what you're going to say, then you realize your audience is waiting for you to say something. It's a self-stoking sort of thing, where the block creates the block. So you just stop."

He didn't leave home after that. Shortly thereafter, he stopped functioning for good. He was exhausted but couldn't sleep; he sat on the floor and held his cigarettes until they burned into his fingers and the resulting blisters extinguished them. His wife called the police. "What was running me was not internal motivations but external. And suddenly I was letting those external motivations go."

He still doesn't like Chicago, and speaks of the city with scarcely disguised horror. "After I'd been there a while, it started to close in on me, like an enormous trap. It has some skyscrapers, but its basic dimension is horizontal -- it just spreads out and out and out. And when you get out there's nothing but dumb cornfields anyway. There is a terror that occurs in Chicago that is worse than any terror I've ever felt."

He's not crazy about New York, either. "He always wanted to fill up with tranquilizers before he arrived," he writes of his alter ego in "Lila." "... It was these crazy skyscrapers. The 3-D. Not just in front of you and in back of you and right of you and left of you -- above you and below you too. Thousands of people hundreds of feet up in the air talking on telephones and staring into computers and conferring with each other, as though it were normal. If you call that normal you call anything normal."

None of this bleak attitude should be taken as a reflection of his own life. He lives a happy middle-class existence. Boring, you might call it. There's a special room at home. There's nothing in it. No computer, no typewriter. Of course, there's no phone. Soundproof floor. Just a chair and some windows overlooking a beautiful valley. There's one little house in sight, which is a bit of a problem: Pirsig can spend his first three hours thinking about who's in it and what they're doing.

"I was thinking of doing an Andy Warhol-type film called 'An Hour in the Life of Robert Pirsig,' " the writer says. "In it, I just sit for a whole half-hour. Then, somewhere around the 36th minute, I raise my hand and write one line. The rest of the hour I just sit there."

Sometimes there's more drama. Sometimes, says Wendy, "he falls asleep."

"I'm going to do a book one of these days about the importance of being blocked," Pirsig says. "A writer who isn't blocked is going to write crap. It means he's writing off the top of his head, he's writing cliches. The way I look at it, a writer should value his blockages. That means he's starting to scale down, starting to get close. A block is a subconscious voice that says, 'Don't sell out by surrendering to the demands of the marketplace.' "

No one would ever accuse Pirsig of doing that. In a 1974 interview shortly after the publication of "Zen," he talked about his next book, which he seemed to think would be finished shortly. "The only people who'll be disappointed will be people who want to be entertained," he said. "I mean, this is going to be a real dull son of a bitch."

The Quest for Quality At 16, your emotions are as raw as they're ever going to get. No one loves you enough, no one understands you, every word is a wound. Conquering the world is your dream, not working for Geico or K mart.

Pirsig was like this. Not only was he rated extremely bright -- his IQ was once measured at 170 -- but there was also the shadow of his father to contend with: Pirsig Sr. was a Minnesota farm boy who, after speaking German until he was 6, went on to get the highest grades ever at the University of Minnesota law school. He then became its dean. His son, majoring in chemistry, flunked out of the same institution.

It was a form of protest perhaps. "Here I am a child prodigy, and I'd like to discover -- I know this is a childish dream -- the secret of life, to know everything there is to know, to be an intellectual master of things. And they're trying to seal me into Wrap and Wax for the rest of my life" -- a reference to a local firm that made wax-coated wrapping paper and employed a number of chemistry graduates.

That conflict was resolved by going into the Army. Like most 16-year-olds, Pirsig quickly abandoned his dreams and became a normal member of society. He married, had two sons, worked for an ad agency and General Mills and then went to Montana to teach. But his dreams returned, focusing themselves on the idea of Quality. And this time he didn't quit. "It was an Indian feeling. When they go on the warpath, there are no restraints at all. It's a good day to die, they sometimes say."

Quality, Pirsig decided, was a crucial ingredient in daily life. The idea that some things were better than others and that these differences mattered powered everything from supermarkets to pro football to the fine arts. But Quality was also something that people didn't agree on. Is it subjective or objective? Why is one piece of art worth $50 million and the other thrown out with the trash? How do you measure Quality, prove that it exists? Everyone feels they know what it is, but no one could adequately define it beyond "what I like."

The short answer Pirsig came up with in Montana and Chicago after exploring many philosophical byways: Quality is neither objective nor subjective. It exists independently, and the fact that we don't realize this is part of the reason the world is in such a mess.

"I became so completely manic. I said, 'My God, I've solved the riddle of the universe!' Of course, anybody who says that is nuts. That's almost a definition of the term. From that moment on, it's been a battle between the original vision and the unbelievingness of the public."

Bantam Books is a believer. The publishing house is said to have paid more than $2 million for "Lila," which means a big push to sell as many copies as possible. Pirsig isn't doing radio or television interviews, a form of reticence that he knows can undercut sales. Yet his hopes are even higher than Bantam's.

He hopes the metaphysics of Quality in "Lila" will be a tool to help people sort out social issues such as abortion. If people are still reading both his books a century from now, he believes "Lila" will be considered more important. He's eager for scholars to pick the book apart, to take it as seriously as Kant or Hegel.

It's a tall order. Most people would feel that, in an increasingly post-print culture, no book could have that kind of effect. But in any case, the author has done his part. He can move on to other things, become for once an easy rider. "The motorcycle's all tuned up," Pirsig says, "all ready to go, and I'm ready to hit the road."

Entering the Illusion

From Robert Pirsig's "Lila: An Inquiry Into Morals":

"... there are times when the culture actually fosters trance and hypnosis to further its purposes. The theater's a form of hypnosis. So are movies and TV. When you enter a movie theater you know that all you're going to see is 24 shadows per second flashed on a screen to give an illusion of moving people and objects. Yet despite this knowledge you laugh when the 24 shadows per second tell jokes and cry when the shadows show actors faking death. You know they are an illusion yet you enter the illusion and become part of it and while the illusion is taking place you are not aware that it is an illusion. This is hypnosis. It is trance. It's also a form of temporary insanity. But it's also a powerful force for cultural reinforcement and for this reason the culture promotes movies and censors them for its own benefit.

"Phaedrus thought that in the case of permanent insanity the exits to the theaters have been blocked, usually because of the knowledge that the show outside is so much worse. The insane person is running a private unapproved film which he happens to like better than the current cultural one. If you want him to run the film everyone else is seeing, the solution would be to find ways to prove to him that it would be valuable to do so, Phaedrus thought. Otherwise why should he get 'better'? He already is better. It's the patterns that constitute 'betterness' that are at issue. From an internal point of view insanity isn't the problem. Insanity is the solution."