In the acknowledgements section of his strange new group biography of six famous musicians who died at the age of 27, Howard Sounes writes about setting out "to see what, if anything, the 27 Club amounts to apart from a series of coincidental and tragic deaths". That "if anything" would be tantalising in an introduction but, after 300 inconclusive pages, it feels rather like an admission of defeat.

Sounes, who has written admired biographies of Bob Dylan, Paul McCartney and Charles Bukowski, is a tenacious researcher. If you want someone to expose the chequered financial history of Winehouse's father Mitch or stack up air miles visiting stars' old acquaintances, then he's your man. But his belief that Amy Winehouse's two-album career couldn't sustain a proper biography leads him on a treacherous detour through the equally short, albeit more productive lives of Jimi Hendrix, Jim Morrison, Janis Joplin, Brian Jones and Kurt Cobain. The "27 Club" (Cobain's grief-stricken mother famously referred to "that stupid club") is such a shaky concept that Sounes ends up dismantling it from within.

So there are really two books here and the good one, the Winehouse one, puts the existing cut-and-paste biographies to shame. Despite resistance from the singer's inner circle, numerous friends and colleagues are interviewed, including her notorious ex-boyfriend Blake Fielder-Civil, myths debunked and facts unearthed, including her final boyfriend's surprising claim that she'd been offered a role in Mad Men. It's a painfully thorough tale of wasted potential: she fell out of love with her own talent.

Winehouse's story is broken up by well-researched potted biographies of the other five musicians, connected only by generalisations that apply to hundreds of performers. Great pain can inspire great art. Drug addicts are often self-loathing. Success doesn't make you happy. When Janis Joplin writes to a fellow heroin addict, "I want to be happy so fucking bad," Sounes adds: "One can imagine Amy saying the same." One can imagine every addict in the world saying the same. He quotes Al Alvarez's description of drug addiction as "gradual, chronic suicide" in a chapter on Brian Jones despite the example of many long-term drug-users, including Jones's bandmate Keith Richards, who proved themselves loth to die. For every possible pattern, you can concoct an equally convincing opposing theory; for every victim, there are countless survivors.

So, why 27? It remains a mystery. If there is any scientific research to explain why it's a particularly volatile age, then it is not included here among all the broad-brush quotations from the likes of Nietzsche and Kierkegaard. Sounes painstakingly demolishes conspiracy theories and other forms of magical thinking but offers no persuasive alternative. It simply seems that some gifted musicians are unhappy, some of the unhappy ones become addicts, some of the addicts die, and some of those do so at 27. The longlist of 27 Club members in the appendix sinks the concept for good. Grunge musician Mia Zapata was raped and murdered and Big Star's Chris Bell crashed into a telegraph pole, yet Iggy Pop is alive and well and selling car insurance. The terrifying randomness of life is enough to make misty notions of echoes, premonitions and the movement of Saturn seem comforting.

You could imagine a Greil Marcus or Paul Morley feeling energised, rather than embarrassed, by so much chance and uncertainty, happy to extend florid tendrils of prose down rabbit holes of coincidence and myth. But Sounes is too diligent to trade facts for fancy, so he has produced a bizarrely self-thwarting book that represents the gradual, chronic suicide of an author's own premise.