The story of a Jew masquerading as a Muslim sounds like a bad joke. But the story of Lev Nussimbaum, who became Essad Bey and then Kurban Said, is hauntingly true. Born in 1905 in Azerbaijan, the son of a Jewish oil tycoon, Nussimbaum spent most of his life on the run. He was chased by the Soviets, then the Nazis and finally the Italian Fascists. Along the way, the subject of "The Orientalist," Tom Reiss's absorbing portrait of this man and his times, turned himself into a prolific and highly regarded author, with 17 books to his credit, including early biographies of Stalin and Lenin and Azerbaijan's one literary classic, "Ali and Nino." But it was when the teenage Lev passed through Constantinople that his life changed completely: he became enchanted with the Muslim world. What he fell for was more ideal than reality--an egalitarian fantasy world of Christians, Muslims and Jews. But he wasn't just playing dress-up. Steeping himself in the history and culture of Islam, he did everything he could to transform himself into a Muslim prince, and became a poster boy for the shape-shifting identities that characterized Europe between the world wars. Nussimbaum's distinction was merely to be more flamboyant than--well, just about anyone.

"The Orientalist" is not without its faults. Reiss comes off as one of those people who, when you ask where you can mail a letter, start by giving you the history of the Postal Service. Where a few pages of background on the Weimar Republic or Russian emigres would suffice, he throws in whole chapters. As a result, Nussimbaum disappears for pages at a time. That's a shame, because as long as Reiss sticks with his Orientalist, he has a fascinating story to tell and he tells it well.

The final chapters, in which an impoverished Lev moves to Italy, hoping to write an officially sanctioned biography of Mussolini, are heartbreaking. With only a couple of years to live--he would die in 1942 at the age of 36--he took up residence in Positano. Suffering from Raynaud's syndrome--a circulatory disease with gangrenous effects--he subsisted on morphine, hashish and the kindness of strangers. And always he wrote, scribbling his memoirs on any scrap of paper he could find, including cigarette papers. The locals knew him only as "the Muslim," but a half century after his death they remembered his exquisite manners, which were, at that point, about all he had left. In one of the last letters he wrote, when he was having trouble keeping things straight, he told a friend, "Don't be frightened--but I regret to tell you with all formality that I have lost my mind." He sounds like the hero of some too-fantastic movie, or of one of his own romances. It is to Reiss's considerable credit that in the pages of "The Orientalist," Lev Nussimbaum/Essad Bey/Kurban Said comes to life as altogether, albeit bizarrely, human.