No answers, my friend, but a lot of wind

Bob Dylan, Behind the Shades: take two by Clinton Heylin (Viking, £20)

Updating the biography he wrote a decade ago to mark Bob Dylan's 50th birthday presented Clinton Heylin with a problem. What tone should he adopt this time? "Judas or Peter... Or perhaps I am to play Paul, a man of strong opinions and fixed views, whose 'version' of his philosopher-king coloured posterity's view more than any interpreter of the tablets who had known their author first hand?"

Updating the biography he wrote a decade ago to mark Bob Dylan's 50th birthday presented Clinton Heylin with a problem. What tone should he adopt this time? "Judas or Peter... Or perhaps I am to play Paul, a man of strong opinions and fixed views, whose 'version' of his philosopher-king coloured posterity's view more than any interpreter of the tablets who had known their author first hand?"

Such delusions of grandeur! The notion that the gospel according to Clinton will be revered years hence is laughable. Neither does he play Peter. The role that fits best is Judas.

Heylin has done rather better than 30 pieces of silver, though the principle remains. And there's a betrayal of sorts of his publisher, who probably hoped for more dirt than is dished. There are quite a few entries under such titles as "cruel streak", "drinking", "drug habit" and "secret wives", but Behind the Shades falls (mercifully) far short of Albert Goldman.

Heylin has revised, or at least recast, his previous effort. In his blinkered way, he has brought Dylan's story up to date. Yet sex, drink and drugs are essentially what's new about this book. It reveals nothing not already obvious: those "wild" Sixties concerts were done on a mixture of heroin and speed, those in the Seventies on coke, the later ones on booze. One can imagine acquiring a taste for Jack Daniels, but sambuca?

As to girls, big boobs are favoured, while the presence of so many wailing women on later albums is explained by Dylan's preference for the casting couch. Heylin is unsure how many children there are. Feminists have long branded Dylan a misogynist. Here is evidence beyond the songs.

So far, so what? Where this portentous tome really irritates is with the haughty dismissal of writers such as Robert Shelton, the New York Times critic who gave Dylan his first review and helped launch his career. Here I must declare an interest. I knew Shelton from 1979 until his death in 1995 as he agonised over his long-overdue Dylan manuscript. Its various publishers pressured him to "tell more" (ie dish the dirt). Inevitably, given the weight of expectation, what was published in 1986 disappointed many. But No Direction Home will come to be seen as a classic. Shelton put Dylan's life in context. Heylin's Dylan works in a vacuum. True, he makes frequent mention of Rimbaud but does not adequately credit Shelton and others who got there first.

No Direction Home was weighted towards the Sixties because Shelton believed - rightly - that those were the key years. Behind the Shades gives equal weight to everything. Rather than interpreting, Heylin merely joins together quotes from those who have known Dylan. Moreover, he does so without proper notes, which goes some way to disguising the fact that much material is far from original. The provenance of notebooks and diaries remains unclear.

Heylin's approach fails to separate wood from trees. All but the most ardent trainspotter will find his endless list of what songs were played at which gigs tedious. When he ventures beyond that, his critical faculties are called into question. Someone who can praise Under the Red Sky (1990) while dismissing Another Side of Bob Dylan (1964) as having only "the kernel of a fine album" has no credibility. Finally, there's the small matter of style: Heylin can't resist touches of Dylanese (outta, kinda, ol'), tabloidese (Fab Four) and the merely awful ("Dylan's thoughts turned to returning to the maelstrom known as Manhattan"). Metaphors are mixed, sense is lost or never made.

At the end of 720 undisciplined pages, Heylin offers no real conclusion, merely the acknowledgement that Dylan's golden age is past. The central question of why a wealthy 60-year-old should wish to tour endlessly, deconstructing his songs and thus his "legend", is never answered. Why he matters at all is never made clear.

The reviewer's 'Dylan Companion', co-edited with David Gutman, appears in a new edition next spring from Da Capo