BOOK REVIEW / FICTION : A Thriller in Which Fiction Is Biography : THIEF OF LIGHT <i> By David Ramus</i> ; HarperCollins $23, 320 pages

David Ramus’ first kill, a genius of a master painter-cum-art forger, is dispatched with a generous helping of blood and mayhem in the prologue to his first novel, “Thief of Light.” The mix of paint on canvas and blood everywhere else sets the tone for the rest of this fast-paced riot through Manhattan’s tony homes, pricey art galleries, sordid streets and corpse-filled Dumpsters.

There have been lots of thrillers about the art world, but this one rings with authenticity, perhaps because the author was a high roller on the art scene a decade ago. He was also a heroin addict, and he has used three experiences to recreate a metropolis in which the big-money buyers are members of a Japanese Mafia that makes the old-fashioned Sicilians look positively sentimental. Ramus has done a fine job of characterizing his Asian cast, all men who play a broad range of interesting roles, some likable, some not.

The forger’s death, together with the destruction of his new “Monet,” sets the action in motion. Adrian Sellars, his partner in the relatively low-level crime of forgery, finds himself behind the eight ball. The Japanese buyer who expects the Monet refuses the return of his down payment. He demands a Monet, fake or real, and threatens, should Sellars’ fail, to kill his young daughter.

Sellars has to comply. But how? One murder leads to another and within hours Sellars loses his other partner (the friend with whom he owns an art gallery) when a master Japanese thug sends a bullet through his head.

The people left in Sellars’ shrinking universe of friends include the beautiful woman who supplies his heroin addiction, and the even more beautiful, brilliant, rich, young woman who has been working as a receptionist in his gallery. While one woman betrays him, the other comes to his rescue, and the pace mounts. With love blooming, Sellars is now vulnerable on two fronts--the daughter and the lover.

Money is never a problem to Sellars because his obligations are in the multimillions--simply beyond his reach. His debts do not stop his access to credit cards and taxicabs and the lifestyle of the more than well-to-do. With echoes of Lovejoy, the English detective-cum-antique dealer who experiences some magic frisson every time he is in the company of a genuine antique, Sellers goes slightly bananas in the presence of the “real thing,” a genuine Monet, for instance, or the Gauguin that decorates the foyer of the gangster’s mansion on East 72nd street.

It is hard to separate the novel from the life of the author. Its verisimilitude--the details of dealings and dirty work in the art world, both buyers and sellers--and the subculture of dope have the ring of truth. The author explains that he wrote “Thief of Light” as therapy, and in the hope that it might fill his empty coffers. Once committed, he wrote fast, looked at what he had done and, like little Jack Horner, found that he, too, had pulled out a plum.

So he found an agent who sent it directly to HarperCollins. An editor there offered half a million dollars, and doubled the offer at the threat of losing it. What he did not reveal to his publisher (and which his publisher turns out to delight in) was the extent to which the scams he described as fiction were akin to the scams he perpetrated on art dealers and collectors, some of whom thought he was a friend. Between them, Ramus still owes some millions of dollars.

In May, a federal grand jury indicted Ramus on charges involving converting more than a million dollars worth of paintings to his private coffers. Wherever he may wind up, he is presently on a book tour and proving what few Americans have any more need of proof: that larceny and mayhem are highly negotiable and that the free market offers pay dirt to the lowest common denominators--if they tell it right.

Ramus is a fine storyteller. He dangles his hero and heroine’s fate over the abyss more than once, but readers know that they will pull through because they are both super-ingenious--and besides, that is his responsibility.

A natural storyteller, however, is not a natural writer. So awed were his publishers with this raw, tale-spinning talent that they apparently offered no editorial assistance. The prose is heavy with cliches, the ripening love affair wooden and perfunctory, and the female characters direct from the back lot. No matter, these shortcomings pale in the shadow of Ramus’ ability to keep us turning the pages.

Already out on audiocassette, “Thief of Light” is good, lightweight entertainment that will happily fill a cross-country flight. We can cheer the poor-little-rich-boy junkie who, belatedly, develops integrity and saves a handful of lives and souls, including his own. Whether this book will save its author from jail or from the modern equivalent of debtor’s prison will have to await the sequel.