IT GOES WITHOUT saying that Peter De Vries is terrifically amusing in this, his 21st work of fiction. As in many of his recent books, he tells in Slouching Towards Kalamazoo the instructive tale of a young person from the heartland who encounters the sexual revolution in all its baffling glory and who pays the price for its pleasures: "What a mess! What a shambles I had made of my life just for an ankle down the old primrose path!" It is a tale of innocence and carnality, a mix both explosive and hilarious, and the wily De Vries milks it for every available laugh; but it is also a tale of sober and sobering aspects, and these too De Vries explores with characteristic subtlety.

The innocent of the tale is Anthony Thrasher, a.k.a. Tony, a.k.a. Biff, who as the story begins is a 15-year-old eighth grader, a classic and chronic underachiever, residing in "my North Dakota home town, which I will call Ulalume." His teacher, Miss Maggie Doubloon, is a luscious peach soon to turn 30, in whom "I seemed to sense a burning wish to Live, certainly to enjoy a life far richer than she was now, a self-realization for which getting the hell out of Ulalume would be only the beginning." As part of her curriculum Miss Doubloon decides to teach The Scarlet Letter, and soon enough she goes ahead and lives it. As a consequence of a one-night stand she enjoys with Tony while tutoring him in history and biology she becomes pregnant; with that, De Vries is off and running into this highly irreverent modernization of Hawthorne's scandalous classic.

To say that one thing leads to another is, to put it mildly, an understatement; orderly plotting is not among De Vries' strong points, and he permits Slouching Towards Kalamazoo to drift in any direction it chooses. Thank goodness. With De Vries the rule is serendipity, not structure. Characters wander in and out not in order to contribute to the overall movement of events but so that De Vries can get this observation or that off his chest. There's the professor, for example, Dr. Chevrolet, "one of those academic capons whom a lifetime of unchallenged pontificating in the classroom has left with the conviction that they are also arresting outside it," a gentleman who "must have been well into his sixties, fleshy and ruddy, with a hooked nose on which you wanted to plant a pince-nez to complete a general sense of stereotype." There is Maggie's landlady, Mrs. Clicko, who "was so tiny that on all fours she would have made a nice trivet," and for whom Tony imagines a dreadful end:

"Slinging Mrs. Clicko over my shoulder in the fireman's carry, I staggered up a ramp contrived of two planks set together between the street and the tailgate of the truck, and dumped her into the maw of the Port- O-Mix, where after a number of revolutions she finally dissolved into the slip-slopping sludge, for eventual disappearance in the floor and walls being poured by the workmen. 'A concrete solution,' I murmured. . . ."

Through all of these amusements marches the figure of "indomitable Womankind," after which every male created by De Vries is forever panting: "I have suffered at its hands seduction, scandalmongering, chicanery, garrulity, silence, false witness, non sequitur, prune whip, and quotation out of context, but respect has endured and affection prospered." That isn't the half of it. Enter Bubbles Breedlove:

"She was a buxom girl, with whorls of honey-colored hair to her shoulders, and a mouth like the inside of a jelly doughnut. I don't mean to offer that as a simile, only to report a mental association. No grossness is implied, such as the overapplication of lipstick. Far from it. Only a crimson sumptuosity. We had here a wide, generously molded, rubbery orifice, such as made one think of long, drenching kisses draining the sap from one's bones, hours of slobbering bliss. What a swine one is, one thinks, loftily. And do one's rippling muscles remind her of writhing adders as one toils, shirtless, in the blazing sun? A youth glistening in the morning of his manhood? A mouth like the inside of a jelly doughnut."

But Bubbles comes later in the story: after the invention of the modern T-shirt business by Maggie Doubloon; after the birth of her son, Ahab; after the great debate between Tony's pious father and Doc Mallard, an atheistic dermatologist; after the break-up of Tony's parents' marriage and his mother's subsequent marriage to Doc Mallard; after Tony's delivery of "the coup de grace to the Puritan ethic," leaving it "dead as a doornail at our feet, laughed to smithereens"; after Tony's father's formulation of "Christian atheism," which Tony considers "the most tolerable accommodation of faith and reason to each other for our time, providing a discipline of belief and necessary ethical imperatives on the one hand, and intellectual realism on the other."

And here it is that De Vries turns serious. In Slouching Towards Kalamazoo as in so much of his previous work, questions of faith lurk beneath the frolic and fun. When the great debate between the minister and the atheist causes each to convert to the other's credo, and then when a second confrontation further muddles matters, De Vries is left to observe: "Voltaire was right. If there were no God, it would be necessary to invent one. And invent Him mankind jolly well had, to see him through this vale of tears." It is not an original observation, but this in no way diminishes its profundity:

"So then. We shall no longer like college sophomores in a dormitory bull session labor the importance of illusions to human endurance, shall we? We shall simply take it for granted, and howl and simper and snivel and roar no more. There is a point beyond which the poor dumb beast simply cannot be pushed, without some sustaining myth. Belief without an intellectual foundation is better than none at all. Aren't you 'saved' if you think you are, considering that, gone, you'll never know the difference anyway? Think of the millions now dreamless dust, whose passage from life to death myth has erased, like mountain travellers traversing a bridge of snow and ice safely spanning an abyss of whose existence they were blessedly unaware."

No doubt it is because Peter De Vries so acutely understands the sadness of this vale of tears, and the capacity of hope and illusion to ease our passage through it, that he is our finest contemporary chronicler of the human comedy. If it is true that there is no funnier novelist now writing in America, it is equally true that there is no kinder one. This, in the end, is why we read him.