Photographer Cecil Beaton knew where Mick Jagger's power resided. "The mouth is almost too large," he wrote. "He is beautiful and ugly, feminine and masculine. A rare phenomenon." In that mouth, granted pop-art immortality by John Pasche's Rolling Stones logo, you see Jagger's voracious, infectious appetite. Although he briefly delighted the left with a spasm of '68 radicalism during which he declared, unbelievably, that "there should be no such thing as private property", he had no real affinity for the utopian side of the 60s. He embodied instead the pushy, hard-charging aspect that said that the time for waiting was over and the time for taking was here. His raw desire had a certain brutal purity, and this PE teacher's son combined it with a muscular discipline that ensured the band's improbable longevity. As the US critic Robert Christgau remarked: "He wanted everything, and he was arrogant enough to believe he deserved it."

Unfortunately, these qualities lose their charm with age. Nearing 70, Jagger's piratical foil Keith Richards is fondly regarded as a species of one  homo rocknrollus  while Jagger is seen as the face of Rolling Stones plc. "I want people to think of me as a fucking great performer," he once complained to Atlantic Records boss Ahmet Ertegun. "I mean, Keith doesn't have to worry about this shit. I'm Ebenezer Scrooge, and Keith's the pure artiste. Everybody loves Keith."

Christopher Andersen's second biography of Jagger, timed for the band's semicentennial, is likely to make those famous lips twist further downwards. Following Keith's rapturously received memoir, Life, the less forthcoming Mick must settle for this diligent trawl through his dirty laundry. Serial bestseller Andersen pursues subjects almost as energetically as Jagger pursues women, and he knows his audience would rather be privy to the bedroom than the recording studio. "Drug-fuelled antics" and "amorous escapades" abound. The making of the Stones' decadent masterpiece Exile on Main Street merits one page while Jagger's unsuccessful pursuit of a young Angelina Jolie extends across four.

The Jolie story is one of Andersen's big scoops; another is his apparent (though not watertight) confirmation of Jagger's early 70s affair with David Bowie. By the last page it seems quicker to list the people who haven't fallen into Jagger's arms at some point. Only Truman Capote was entirely immune to the singer's magnetism, describing him as "about as sexy as a pissing toad". Armed with many interviews and secondary sources, Andersen presents every lurid tale with a certainty that the cautious reader may not share.

It's not just the minor errors that ring alarm bells  blues musician Alexis Korner becomes Alex Korner, late guitarist Brian Jones's girlfriend Anna Wohlin turns into Anna Wholin  but the selection of material. Andersen takes a line from Richards's Life seemingly to support his retelling of the old myth about Marianne Faithfull and the Mars Bar but ignores Richards's insistence that it never happened. The author also argues that the song Angie is about Bowie despite Richards's own account of how he, not Jagger, wrote most of it. But then Andersen concedes nothing to doubt. You wouldn't think the subject of Carly Simon's You're So Vain was one of pop's most famous mysteries from the way Andersen bluntly states (despite Simon's own denials) that it's Jagger.

Andersen's initial promise to reveal a "mind-spinning tangle of contradictions" never materialises. Brick by brick, he builds an impermeable impression of a ruthless, controlling, disingenuous narcissist. Every interviewee speaks in neat, damning soundbites. Former publicist Keith Altham: "He doesn't have much loyalty. People come and go swiftly, and are decimated." Ex-lover Marianne Faithfull: "Mick basically has contempt for women. They only exist as reflections of him." A wounded Keith Richards: "He used to be a lot warmer. He put himself in the fridge."

But the reader can't hope to understand Jagger or his band without an insight into the songwriting  you know, that eccentric thing musicians do when they're not bedding leggy lovelies. It's clear when Andersen glibly sums up the complex, self-questioning Street Fighting Man as an "anthem for placard-waving, rock-throwing demonstrators from Berkeley to Paris" that the substance of Jagger's lyrics is of no interest to him.

A book about a singer that pays no attention to his songs is simply an anthology of gossip, albeit juicy, unusually well-researched gossip. It ends up presenting the man whose idiosyncratic genius helped define rock stardom for half a century as little more than a superannuated sexual predator with a shrewd investment portfolio. Many of the harsh things people say about Jagger in these pages may indeed be true, but he deserves better than this.