Leroy Neiman's gift: capturing the action of sport - but is it art?; Winners, by Leroy Neiman. New York: Harry N. Abrams Inc. 350 pp. $85.

Leroy Neiman's new book, ''Winners,'' is a blockbuster coffee-table extravaganza with 350 large pages, all in full color. It is Mr. Neiman's view of the American sport scene over the last 30 years. Its pages are laced with paintings, drawings, and snapshots of Mr. Neiman with a wide variety of sports personalities, and a rambling anecdotal text by the artist.

Neiman is a ubiquitous popular artist, whose career was launched early on by Playboy magazine and furthered by his appearances on ABC television, largely in relation to ABC's coverage of the Olympics. He has a knack for appearing at fashionable places with fashionable people, always bedecked in flamboyant clothes, prominently displaying his broad-brimmed fedora, cigar, mustache, and sideburns. If the photos in the book are to be believed, he even plays tennis with cigar and hat. Mr. Neiman's work is exhibited and sold by such diverse organizations as Burger King, Hammer Galleries, and the prestigious Knoedler Galleries.

It's easy to understand his far-ranging popularity. His work is colorful and lively, and his subject matter, the world of sports, is fascinating to millions of fans and amateur participants. As a popular artist, Mr. Neiman is, himself, a winner; his prints sell in the millions of dollars a year. But a book as large and extensive as this invites us to take Mr. Neiman seriously as an artist, and at this point problems arise. One begins to sense that much of his work is too facile. His sports figures float in a plethora of palette-knifed pigment straight from the tube. The effect is one of fantasy. There is none of the gritty reality of such great sports painters as Thomas Eakins, George Bellows, or John Groth. Mr. Neiman's painting technique is suited to the lighter, airier sports, such as skiing or cycling. There is a marvelous painting of a bike race in Paris. But football, boxing, and baseball demand more sub-stance.

An artist who draws action on the spot, as Mr. Neiman does, can be forgiven some misses among the hits; it is a risky business. But there are an inordinate number of misses in this book. Mr. Neiman would have been better served by some stringent editing. No artist should bring all his work out of the closet.

One is also hard put to find here a growing artist. The work covers 30 years, but it is difficult to find early, middle, and late Neiman. He has been trapped by the commercial success of his technique. All the work has a sameness that palls after a couple of hundred pages.

Mr. Neiman is most ill-served by his text and the photos that are scattered through the book. Although early on he professes an interest in the little man - the waiter, the stablehand, the chauffeur - the impression given is one of superstar worship and high-school-yearbook elitism. The book is called ''Winners ,'' but even in the world of sport there are other gauges of success than stardom. Mr. Neiman has spent little time seeking out the values of life not apparent through the television lens.

Perhaps it is this feeling of skimming the surface in art, text, and photos that leaves a dissatisfaction with this book. Mr. Neiman has abundant energy and an uncanny ability to be on the scene for major events. One wishes for a more probing and perceptive eye and a more studied, thoughtful result.