Miss Shirley Bassey by John L Williams

Most of the time, debate about the function of biography is marked by woolly but polite consensus. Then, every few years, a book is published which shifts that debate up a gear. It might be a particularly vicious example of the form, such as Roger Lewis's life of Anthony Burgess, or one where there's been an obvious tug of war for control of the narrative, such as Anne Stevenson's Sylvia Plath biography Bitter Fame. Or it might be one that reveals more than its subject's admirers feel comfortable knowing: Andrew Motion's Philip Larkin: A Writer's Life, for example. Even there, though, there was a good, old-fashioned artist's-life-informs-the-art case to be made. (One certainly reads "Lines on a Young Lady's Photograph Album" – "[I] wonder if you'd spot the theft / Of this one of you bathing" – with an extra frisson, knowing its author was addicted to schoolgirl porn.)

But why do we need to know that Shirley Bassey's Nigerian father was imprisoned and then deported for raping a child? Dame Shirley might be 73, but she's as busy as ever. She played Glastonbury in 2007 and last year released a new album with songs written for her by high-profile fans such as Pet Shop Boys and Rufus Wainwright. Why should she be dunked in this mudbath?

There are two answers, neither terribly satisfactory. One is that her father's offence, while never revealed by the media, has for years been an open secret in the area around Cardiff's Tiger Bay where Bassey grew up. (Doorstepped by John Williams, old acquaintances of the family asked hesitantly: "You know about her father?") Also, all the relevant documents were in the public domain, so journalists' silence on the subject becomes, for Williams, not a laudable moral reflex but a sin of omission.

The other – not a bad answer, but pretty specious – is that full knowledge of the harshness of Bassey's impoverished childhood can only enhance our admiration for her achievements (more than 100m records sold; a damehood; being sent up by Morecambe and Wise). Throughout, Williams juggles these justifications as one might a pair of overripe plums. Then, in a strange epilogue, he signs off with the platitude that "acknowledging truths, even hard truths, is in the end helpful to all concerned". Well, yes. But then again: no.

Perhaps the reader would feel differently if Miss Shirley Bassey had a clearer agenda. In most respects, it's a conventional (and effective, and insightful) piece of musical sociology. It's rigorous and scholarly on the racial context of 1950s Britain; on what being mixed-race would have meant for Bassey and how, even when she visited America, colour was not an issue for her as it was for more established black stars such as Sammy Davis Jr, who weren't permitted to stay in the hotels where they were performing. The chapters on her childhood, spent among the brothels of Bute Street, where she was the youngest of 10 and her parents made money organising "rent parties" for sailors, are sensitive and empathetic without being prurient.

When she moves to London, Williams wheels on the spivs and sharks who went to work on skinny, spotty Shirley, teaching her stagecraft and pointing her in the direction of the big time. Lovely details abound. The engineer on Bassey's debut single, the breathtakingly obscene "Burn My Candle (At Both Ends)", was a young Joe Meek. To hold that long note at the end of "Goldfinger", she had to remove her bra to increase her lung capacity.

More generally, Williams works hard to defend Bassey against accusations of divadom and the criticism that she abandoned her roots – all this despite the fact that he isn't, in any straightforward sense, a fan of the woman or her music.

So what's the problem? First, the book is structurally misconceived. A David Peace-style "fictional documentary" interlude, taking us inside the head of her gay husband/manager Kenneth Hume, feels like an experiment Williams couldn't bring himself to discard. Then, in 1969, he brings down the curtain, declaring that he can't be bothered to continue because what follows is "too familiar to need rehearsing here: it's the Shirley Bassey of the popular imagination, the larger-than-life Shirley Bassey of endless tours and TV specials and chat-show sofas". The sheer arbitrariness of this is baffling. It isn't just a cop-out, it's plain wrong – like ending a biography of David Bowie in 1999 because that's when he had his wonky teeth fixed.

And second, its tone is that of a posthumous biography. It put me in mind of Ted Hughes's remark – made, admittedly, in a specific, charged context – that biographers can "no longer feel the difference between the living and the dead". This is why one feels so uneasy reading Miss Shirley Bassey and why, for all its real strengths, it might be better if it hadn't been written.

John O'Connell is co-author of The Midlife Manual (Short Books).