"The sixties were the "sex, drugs, and rock-and-roll" era, and Andy Warhol was its cultural icon. Painter, filmmaker, photographer, philosopher, Warhol was both celebrity and celebrant, the man who put the "Pop" in art. His studio, the Factory, where his free-spirited cast of "superstars mingled with the rich and famous, was ground zero for the explosions that rocked American cultural life. And yet for all his fame, Warhol was an enigma: a participant...