Leo Castelli reigned for decades as America’s most influential art dealer. Now Annie Cohen-Solal, author of the hugely acclaimed Sartre: A Life (“an intimate portrait of the man that possesses all the detail and resonance of fiction”—Michiko Kakutani, The New York Times ), recounts his incalculably influential and astonishing life in Leo and His Circle .

After emigrating to New York in 1941, Castelli would not open a gallery for sixteen years, when he had reached the age of fifty. But as the first to exhibit the then-unknown Jasper Johns, Castelli emerged as a tastemaker overnight and fast came to champion a virtual Who’s Who of twentieth-century masters: Rauschenberg, Lichtenstein, Warhol, and Twombly, to name a few. The secret of Leo’s success? Personal devotion to the artists, his “heroes”: by putting young talents on stipend and seeking placement in the ideal collection rather than with the top bidder, he transformed the way business was done, multiplying the capital, both cultural and financial, of those he represented. His enterprise, which by 1980 had expanded to an impressive network of satellite galleries in Europe and three locations in New York, thus became the unrivaled commercial institution in American art, producing a generation of acolytes, among them Mary Boone, Jeffrey Deitch, Larry Gagosian, and Tony Shafrazi.

Leo and His Circle brilliantly narrates the course of one man’s power and influence. But Castelli had another secret, too: his life as an Italian Jew. Annie Cohen-Solal traces a family whose fortunes rose and fell for centuries before the Castellis fled European fascism. Never hidden but also never discussed, this experience would form the core of a guarded but magnetic character possessed of unfailing old-world charm and a refusal to look backward—traits that ensured Castelli’s visionary precedence in every major new movement from Pop to Conceptual and by which he fostered the worldwide enthusiasm for American contemporary art that is his greatest legacy.

Drawing on her friendship with the subject, as well as an uncanny knack for archival excavation, Annie Cohen-Solal gives us in full the elegant, shrewd, irresistible, and enigmatic figure at the very center of postwar American art, bringing an utterly new understanding of its evolution.