Invisible Republic: Bob Dylan's Basement Tapes by Greil Marcus, Picador pounds 6.99. The critic as mystic: what starts out as a commentary on those famous sessions in the summer of 1967, in the basement of a house in West Saugerties, upstate New York, rapidly becomes an underground history of the American soul as Marcus teases out the story that America tells itself. Dylan's music is treated as - how best to put this? - the plughole down which American history, literature and folklore swirl: Herman Melville and Alexis de Tocqueville bob around with Leadbelly, Sam the Sham and the Pharaohs, and the West Virginia Mine War of the 1920s. It is undoubtedly pretentious; what`s …