From Andy Warhol to Lonelygirl15, modern media culture thrives on the traffic in counterfeit selves. In this world the greatest artist will also be, almost axiomatically, the biggest fraud. And looking back over the past 50 years or so, it is hard to find anyone with a greater ability to synthesize authenticity — to give his serial hoaxes and impersonations the ring of revealed and esoteric truth — than Bob Dylan.