SOMEONE ELSE'S MONEY, Michael, Thomas' new novel, is a vast, ambitious fable which paints an incisive and decidedly unflattering portrait of a large slice of American life. Thomas takes the reader backstage to show him the elaborate shell games that go on in the interlocking worlds of big money and high culture.

The two foci of the novel are a Wall Street brokerage house and financial services complex called the Seaco Group, and a New York art museum, the Fuller Institute, which appears to be a cross between the Frick Museum and the Morgan Library. Both are targets of similar "takeover bids," and the splendid gallery of grotesques that Thomas creates are generally involved in the battles for control of both Seaco and the Fuller.

A Texas multibillionaire named Buford "Bubber" Gudge IV, for example, formulates an elaborate con game which will involve Seaco in a huge financial commitment to two entirely fictional companies. If successful, Gudge's plan will wipe out Seaco and cause severe repercussions all over Wall Street. These, however, are only secondary goals for Bubber; his real aim is the destruction of his half-sister, Granada Masterman.

Granada, a fierce gargoyle who has carved out a financial empire of her own, is trying to gain control of Seaco. She also has designs on the Fuller Institute, where the founding triumvirate of Seaco are all trustees. Eventually Gudge's wife Caryn, a pretty, empty-headed refugee from Odessa, Texas, whose social ambitions eventually rival her carnal appetites in voracity, also becomes interested in the Fuller Institute as a useful conquest in her social blitzkrieg. The choreographer of the danses macabres that go on in the worlds of art and finance is a public relations genius named Sol Greschner. Greschner, a fascinating character loosely modeled after the late Ben Sonnenberg, is one of those paradoxical people who is at the same time a master manipulator of others and yet curiously lonely and alienated himself.

The "hero" of the novel (and the word needs quotation marks) is the art dealer Nicholas Reverey. Although forced by his profession to navigate the thoroughly polluted waters of the rich and socially ambitious, he maintains his integrity through a genuine dedication to and understanding of art. One of the great virtues of the novel, indeed, is the authority with which Thomas portrays art and the art world. For example, when he describes an invented series of Rubens oil-sketches, he is totally convincing, not only in his evocation of the works themselves, but of the commission as a whole, the iconographic meanings they symbolize, and the artist's patrons and stylistic development. Thomas has been an art historian as well as a Wall Street broker, and his expertise in both fields is clearly evident.

For the characters in Thomas' book a real love of art provides redemption, if not salvation. Frodo Crisp, the head curator of the Fuller Institute, might cut a laughable figure gyrating spasmodically to the music in a gay disco, but he is deadly serious--and very sympathetic--when in the thrall of a great work of art. Harvey Bogle may be a vulgarian and a brutal opportunist in the financial world, but he is forgiven many of his sins by his conversion to art collecting, and by his "natural eye."

Someone Else's Money is a dense, complicated novel teeming with vivid characters. The author also has strong opinions on a variety of subjects ranging from Swiss hotel-keepers to gossip columnists to fashion fads, and some of his vignettes have a finely honed satiric edge.

Reagonomics and "Reaganethics" (to coin a word) are one target. The "laissez-faire, love- the-rich economics and neo-Calvinist, neo- McCarthyist religiosity of the new order" are neatly skewered in the sanctimonious hypocrisies of Senator Rufus Lassiter, author of the best seller Moral Money and the soon-to-be- published God and Gold.

Thomas also has opinions about "frantic purveyors of literature to an illiterate age." One of these is the delightfully named Esm,e Bogle, whose smash best seller Salon portrayed "the rich psychosexual life of the staff and customers of a high-priced Manhattan hairdressing parlor." There is also the scowling figure of Henry Grappler, author of Plop, a novel that "had become the intellectual banner of adolescents of every age." (In case you missed it, Thomas informs the reader that Grappler has just closed a licensing deal for "fashion versions of lumber-jack clothes and cowboy suits" to be sold under the rubric "Clothes According to Plop.")

Thomas doesn't always make things easy for you. To understand the financial manipulations, it is necessary to wade through a mass of Wall Street jargon about "repo financing," "put-call options," the "off-Fed market" and the like. He will also make a lot of people mad. But in the final hundred pages or so, where all the strands of his story converge, I found it impossible to put the damn thing down.