By the middle of the 1970s, Bob Dylan's position as the pre-eminent artist of his generation was assured. The 1975 album Blood on the Tracks seemed to prove, finally, that an uncertain age had found its poet.Then Dylan faltered. His instincts, formerly unerring, deserted him. in the 1980s, what had once appeared unthinkable came to pass: the "voice of a generation" began to sound irrelevant, a tale told to grandchildren.Yet in the autumn of 1997,...