EVERY YEAR, at Christmas, tinsel is a best selling item. William Goldman's book by that name should help make this year no exception. Like its namesake, Goldman's Tinsel is a lot of bright shiny strands hanging together without much substance. It does what tinsel always does; distracts us from the failures in what lies underneath.

I could pursue this metaphor further, mention that in Goldman's Hollywood book he is festooning a palm and not a pine -- which makes the use of tinsel a lot less effective -- but enough. Suffice it to say that Tinsel is aptly named, and as for myself, I've always loved the junk.

"Junk' is the genre into which Tinsel does not so much fall as leap. I suspect we are meant to mince words about this -- "A man who cares more about his craft than his critics" says the jacket copy -- but I don't mean to do that: William Goldman writes junk. He writes gloriously good junk sometimes and gloriously bad junk other times, but junk always and I suspect that's why I and a lot of other people have read him so faithfully these many years. As Goldman himself observes of his book's protagonist, a movie producer, "He understood the world's need for s - - - and he set about filling that need, but never once when art and commerce came into conflict did art stand a chance."

A taste for Goldman, like a taste for junk food, is something that crops up in adolescence and lingers into adulthood where it takes the form of a periodic binge. Not since Boys and Girls Together has Goldman given his fans something so unabashedly "bad" to binge on. After his more serious books like Marathon Man and Magic, Tinsel comes as an enormous relief. It is the same kind of relief one experiences biting into a Hostess Twinkie after months of eating the new French cuisine.

I am afraid that Goldman will be unfairly accused of having written a "T 'n' A"book. This is simply not true. What Goldman has written is something enormously more rarified than that: a "T" book.

Breasts bobble, jiggle, loom, sag, jut, heave and peek from almost every page of Tinsel. "You're hurting them!" Goldman introduces one character, not two, a charming woman named Pig. "Poor babies, " he finally writes her out. It is the first time I recall an author equating character development and bust development and I must say it struck me as something of a breakthrough. Philip Roth should love this book.

It occurs to me, however, that some people may not be quite so acutely keyed into Goldman's breast motif. Those people may, in fact, fall for the ploy that this book is really about Hollywood and not about breasts. After all, Tinsel tells us right on the dust jacket that Goldman is one of the "best known and most respected scriptwriters in the country today" -- a line that tickled my scriptwriter's heart, comparing favorably, I thought, to being touted as "the best imitation margarine." Scriptwriters by definition are neither "best-known" nor "most-respected," except, perhaps, in Hollywood. I am a scriptwriter and I live in Hollywood and I can assure the reader that this book is really about breasts. There are those who would argue that Hollywood is really about breasts, and it's a good point -- in fact, two of them: if Hollywood is really about breasts, then so is this book.

Ostensibly, Tinsel is about a movie producer who is dying of cancer. Lying in the hospital, reeling from the results of the biopsy, he realizes that all his life he has produced nothing but junk -- gloriously good junk sometimes and gloriously bad junk other times, but junk always. "He lay in the hospital, the despair relentless, and he wished that he could cry honest tears, but of course he couldn't -- even his tears were s - - -."

Armed with this realization, the producer sets out to make one Last, Best Movie about Hollywood and Women and "the corrosive effect the one had on the other." Turns out what he means by all that is mainly Cooper's Droop. (For the uninitiated, Cooper's Droop is an affliction that age and jogging without a bra can inflict on the well endowed.) The movie is to be about the fall of a sex goddess, not just her breasts; but, somehow, Goldman and his characters keep getting the two things mixed up.

"You talking to me?" Pig asked.

"To them," Johnny answered, and he nodded toward her breasts.

The gap -- or should I say the "cleavage" -- between Goldman's talent as a writer and his talent as a thinker is brutally exposed in Tinsel. As his dialogue frequently proves, Goldman is a man who can write like an angel. As his narrative proves equally, however, many of his ideas could dance on the head of a pin. Scriptwriting plays to Goldman's strengths. (We have Butch Cassidy and the Sundance Kid and All the president's Men to thank him for.) The novel plays to his weaknesses.

As Playboy editor Arthur Kretchmer once remarked of another writer, "Leave it to him to find his metier and kick it in the teeth."

Wait a minute. Did I say "teeth?"