The pain in life sentences

January is what they call "a slow time" for books. The shops are quiet, apart from people returning misjudged presents. But this year we have taken down the Christmas lights only to find a pair of juicy political life stories squatting under the branches. All those new year resolutions to take a less avid view of gossip and tittle-tattle have been given a shake as rabid claims about ministerial drunkenness, adultery and financial flummery grab the headlines.

The modern enthusiasm for biography, otherwise known as the ancient appetite for snuffling around in the entrails of other people's lives, continues to be the most powerful motor of our reading habits. And of the many uses of biography, the most reliable is the iconoclastic one - the desire to pour scorn (I mean, "shed light") on the bad habits of the rich or famous. But the simplest and best motive is the urge to narrate lives we do not already know about. Another biographical work was published last week. It made fewer headlines. But it will resonate in readers' minds more deeply and for longer than either the descent of Mandelson or the thoughts of the artist formerly known as Mrs Cook.

The Good Listener, by Neil Belton, tells the story of Helen Bamber, a diminutive 74-year-old Jewish woman few of us would have heard of without this book. In 1945, aged 20, she went to Belsen to help survivors (by listening to their sobs). The rest of her life has been dedicated to helping (also by listening) others blasted by torture. In 1985 she set up the Medical Foundation for the Victims of Torture, which she still runs from offices beneath a railway bridge in North London.

She has not lacked for "clients". Her work (and Belton's book) explores the victims of state-sanctioned, medically applied torture in places such as Chile, Argentina and Uganda. It gives a hearing to the tense, decent and damaged men who returned from Japanese camps after the war. And it reveals the long, slow effort, by a few unsung men and women such as herself, to address the wreckage left behind by the world's ideological power squabbles. It is not a survey or roll-call of torture in our century; you won't find Cambodia in the index. But every quotation is stiffened by the knowledge of pitiless deeds, and the result is a tale that dramatises a defining characteristic of our century: the institutional savagery we moderns are still willing to inflict on our enemies (and even those we merely suspect or fear are enemies).

I was working at Granta magazine alongside Neil Belton while he wrote this book. Clearly, it was neither an easy nor a comfortable task: when he came into the office he had the dazed look of someone returning from a very long trip. But when someone is writing about nasty excesses of torture you do not blithely ask how the book is going. Violence glides into the opening sentence of his preface, as "the bad weather of our century", but this is just a laconic understatement, the first breeze of the approaching storm. There are details later, when he declines to be discreet about what happens in torture rooms, which are hard to read without squinting.

It is a momentous tale, the more so for its humdrum aspect. It traces the career of a woman persisting with uphill work, growing in confidence and resourcefulness as the sad years pass. Belton is anxious to demythologise altruism, which is not a simple shining thing, but "difficult and spiky". Bamber is by no means all sweetness and light, but how could she be? And why should she be? Belton puzzles away at her motives. For him, the mystery is not what drives torturers, but what drives the Bambers of this world: they are rarer, after all. Dismissing the easy answers (the "needy carer", etc) he concludes that her life gave her little choice: "she is so sensitive to emergency that she can be tossed around by it like a cork". Bamber herself rejects the suggestion that she is inspired by anything as neat as a "love of humanity" or any other formula. "A lot of it is about myself," she says. "My need to do it is very strong indeed. And it is not a heroic, or even a worthy need."

Belton does not sanctify her. He records the views of her son David, who in his own way has paid a price for her compulsions. "He believed that she would almost find it a relief to hear that he was not all right, for there to be an emergency so that she could swing into action on his behalf." So if Bamber does emerge as a heroic figure it is only by enriching shallower notions of what it is to be heroic. Bamber is not a dragon-slayer, but who is? In trying to pick a path, she has blazed a trail; in devoting herself to listening, she has grown eloquent. Thank goodness there was someone around willing for a moment to forget about house prices in Notting Hill and do what she did: listen.

'The Good Listener. Helen Bamber: A life Against Cruelty', Weidenfeld and Nicolson, pounds 18.99.