Monty Dylan and the Holy Greil

Invisible Republic: Bob Dylan's Basement Tapes by Greil Marcus, Picador, pounds 16.99; Charles Shaar Murray rejoins The Band

My Life in a Stolen Moment" was the title Bob Dylan gave to a rambling, beat-poetic faux-autobiograhical sketch composed in 1963 for the programme of one of his first major concerts. The particular stolen moment in Dylan's life which obsesses Greil Marcus came later, between 1966 and 1968. This was the long moment that Dylan stole, under the pretext of recuperation from a motorcycle accident, to enable his drifter's escape both from a punishing work-schedule and from the increasingly arduous task of being Bob Dylan.

During that retreat, he spent much of the summer of '67 making music with some newfound friends: the Canadian psychobillies, formerly known as The Hawks, he had adopted as his backing group and who would go on to trade under the name of The Band. Rehearsing and jamming in a rented house in upstate New York, and informally recording their work-in-progress, various combinations of Dylan and The Band explored new songs and old, digging deep into their own private mythologies and the collective unconscious of North America to mine a fresh-minted folklore, simultaneously ancient and modern.

Dylan emerged from the experience shorn of his rock and roll trappings, with the mysterious neo-traditional album John Wesley Harding. For their part, The Band released a revolutionary debut album which established their guitarist, Robbie Robertson, as a major songwriting voice. Never intended for public consumption, some of the material eventually surfaced in bootleg form as The Basement Tapes.

Alongside Nik Cohn and the late Lester Bangs, Greil Marcus is one of the founding fathers of modern rock criticism. Indeed, that the field exists at all in anything like its present form is partially attributable to his pioneering work. Marcus first explored the folk-mythic world of The Basement Tapes in a major essay on The Band which formed one of the cornerstones of his massively influential first book, Mystery Train. He was the perfect - if not the only - choice to annotate the first official release of that music when it was finally offered to the public in 1975. Invisible Republic is the culmination of decades of fascination with this extraordinary achievement. Reading it is an experience akin to viewing those sequences in such movies as Antonioni's Blow Up or Ridley Scott's Blade Runner, wherein the protagonist enlarges and refocuses the background dots of a photograph to reveal new pictures that recontextualise the original.

Marcus's most formidable critical asset is his ability to make unexpected connections. He draws on his knowledge of literature, politics, art and history to tease out the resonances of the topics he addresses. His previous works have used Elvis Presley and the Sex Pistols as crowbars to pry open subterranean vaults of the 20th-century psyche.

The "stolen moment" magnified herein expands to span centuries. That summer snapshot becomes a panorama of the invisible republic of the title: "the old weird America" of Mark Twain and William Burroughs, of high tides and tall tales.

The world of The Basement Tapes exists on a mythic American frontier between "the confessional and the bawdy-house", as Marcus put it in the Mystery Train days. Invisible Republic could have used more of both: as Robbie Robertson recalls those seminal sessions, "We went in with a sense of humor ... it was all a goof."

Marcus does indeed have a sense of humour, albeit one of Gobi-like aridity. A lean, scarred Johnny Cash is described as having, at 33, "a face like cancer", which is about as mordant as you can get. But for all its awesome erudition and vaulting imagination, this epic conflation of secret history and badlands balladry could have made use of some leavening levity.

This is a subject with which the author has not finished, and is unlikely to do so this side of the grave. One senses that the saga of Monty Dylan and the Holy Greil has some distance yet to run.