IT IS HARD TO imagine a more improbable object of public enthusiasm than a novel about handball.

On the face of it, the spectacle of two perspiring primates nudging a rubber ball around a plaster room does not inflame the imagination. And yet this modest, enthusiastic and uncommonly brief first novel is an off-the-wall success. It leads the current list for Pinnacle, with a first printing of 300,000 copies; foreign rights have been sold in England, Germany and Holland; and Samuel Goldwyn Jr. is making it into a movie to be released early next year.

This mudslide of adulation seems doubly perplexing in view of the unlikely characters and their dubious relations. Barry West, 26, is an accountant with a tedious but secure job slinging figures in Rochester, N.Y. He is also a splendid amateur handball player with the stamina of a baling machine: useful qualities at the Rochester YMCA where, we learn, "lust for combat" is "quickly veiled with manners, macho handshakes, and backpats."

One day while playing, West finds himself observed by a mysterious stranger in the gallery. The athletic voyeur is a 50-year-old Jewish-Cherokee orphan alcoholic cripple named Tate Coldiron.Plainly, Coldiron's life has not been entirely happy. And worse yet, auto trouble has trapped him in Rochester while he was en route to one of the handball tournaments at which he hustles games for a living.

Broke and thirsty; Coldiron sees in West both a temporary salvation and a chance to become the locker-room Pygmalion of upstate New York.

He suckers the yound man into a game, beats him out of $125, and then makes him an astonishing proposition: He will train West into the premier handball hustler in the United States in exchange for 50 percent of the earnings. But West demurs, too attached to his job and his lover -- Susan Burnett, editor of Woman's Weekly Magazine , a liberated, libidinous but slightly galling combination of Mary Tyler Moore and Erica Jong who has been encouraging West to be more adventurous.

As Alibrandi puts it, in his absurdly engaging scrambled metaphors, "Susan's nicks were hitting home. She didn't know it, but her constant prods that he cash it all in and go with Coldiron were falling on fertile ground." So when an office flare-up ends West's job, he becomes the full-time pupil of the whiskeyladen master. West learns the lore of the court, undergoes a brutal and celibate training regimen, and is transformed into a human handball machine.

The remainder of the story takes place on the road, as the pair earn more and more money and Coldiron discovers, to his growing horror, that he has created not only the perfect player, but a sort of Frankenstein monster in sneakers. After he discovmonster in sneakers. After he discovers West's murderous flaw, the ball is in Coldiron's court, and his definitive solution makes the book's dramatic end.

As a plot, this is clearly spunky -- if not immoderately subtle. At its best, it is Cat Ballow in reverse; at its worst, it is simply dumb. But despite its preposterously implausible characters and amateur prose style, Killshor scores -- with a certain inescapable narrative momentum which will doubtless provide an exciting movie.

The reason is that, consciously or not, Alibrandi (a former construction-company manager, alcoholism counselor and migratory nonfiction author of Free Yourself, Meditation Handbook, Bio-Rhythm and Young Alcoholics) has made a book which, if not true to life, is true to fantasy.

"Modern cultural education," Dr. Freud noted in Three Contributions to the Theory of Sex , "utilizes sport to a great extent in order to turn away the youth from sexual activity; it would be more proper to say that it replaces the sexual pleasure by motion pleasure and forces the sexual activity back upon one of its autoerotic components."

It is easy to dismiss this as mere Viennese moonshine until reading a book like Killshot , in which the psychofantasy content is so plainly obvious, and so successful.

Coldiron, whose dialogue is rank with masturbation references, makes one thing perfectly clear about West's romance with Susan: "You see her when I say so. I don't want you.... ing away your brains and energy."

The rest of the plot plays the same game. To quote the Oracle of the Psyche again: "In the promotion of sexual excitement through muscular activity, we might recognize one of the sources of the sadistic impulse. The infantile connection between fighting and sexual excitement acts in many persons as a determinant for the future preferred course of their sexual impulse."

Thus it goes with the misfortunate West, as he turns from solicitous lover to secretive sadist. So natural are the psychological stops being played that it rarely occurs to the reader to question this radical transformation, and Alibrandi scarcely needs to discuss the motivation of his four-wall felon.

Nor will the reader, caught up in the psychofantasy, cavil at the hand-in-glove subplots: the otherwise inexplicable "hidden chemistry of desire" which simmers between Coldiron and Susan; or the parallel geriatrico-pedagogical conflict between the Old Guard of the game and the new, slick, corrupt national handball organization.

In the final tally, Killshot is the paperback equivalent of a good B movie. And at the price, it's well worth playing along.