Say what you will about Jerzy Kosinski's fiction, his life was undeniably fascinating -- most often made so by his own diligent and inventive hustling. If you accepted Kosinski's own account, you believed he survived a childhood in war-torn Poland, where he was separated from his parents, on the run from Nazi occupiers and so horribly abused by local peasants that he was, for a time, struck dumb. After emigrating to the U.S. in the late fifties, he swiftly published two works of socio-political nonfiction, then broke through with "The Painted Bird," a novel he strongly suggested was based on his wartime autobiography. Eight other novels followed, including the 1969 National Book Award-winning "Steps" and later "Being There."

Kosinski's fame arrived at a time when the Jet Set was just reaching cruising altitude; he became an enthusiastic frequent flyer. He displayed his considerable gifts as a raconteur on "The Tonight Show," and partied endlessly with the biggest names in the Lit crowd. He dabbled in movies (playing Lenin's pal Zinoviev in "Reds") and politics. And he took pleasure in spreading tales of his dark side: Kosinski the Master of Disguise prowling Manhattan's underworld at night, reveling in the sex clubs that flourished in the days when sex didn't have to be safe, just fun.

But as James Park Sloan recounts in his new biography, Kosinski's frantic life hid a secret: he did not, strictly speaking, write his books by himself. When The Village Voice published, in 1982, the revelation that Kosinski had for years been discretely employing "editors" to polish his poorly written first drafts, his reputation was forever tarnished. Further investigation revealed that Kosinski had the bad manners to pay his collaborators poorly; that his waif-on-the-run story had been taken from, among other sources, the real life of his fellow Pole Roman Polanski; and that he had largely cribbed the plot of "Being There" from a Polish novel of the 1930s. Kosinski limped along, a vastly diminished figure on the edge of his former world, until his suicide in 1991.

It is clear now that Kosinski's most energetic construction was his life, and Sloan's daunting task has been to untangle fiction from facts purposefully obscured for decades. He does this patiently and thoroughly, albeit with a more workmanlike prose style than you'd wish. Kosinski's most useful personal discovery may have been, as Sloan puts it, that "a writer's books. . . are only part of the product. The real -- the ultimate -- product was himself, and the books were, among other things, a vehicle for selling that product." Certainly others -- Hemingway and Mailer come to mind -- have seemed to lead their lives by this rule; it was Kosinski's misfortune that he tried to take self-aggrandizement one step too far. He lost control of his best story.

-- Edward Neuert