How To Be Good is told by Katie Carr, a GP from north London. She views her world with self-deprecating comedy and restive neurosis.

Katie is away on a conference in Leeds, surreptitiously sleeping with an acquaintance, when she shocks herself by asking her husband for a divorce on her cellphone. As a result of this wilful wrong turning in a tired, habitual conversation, all the certainties of her life are replaced by doubts. The first section of this book the terrain is strictly, artfully, full of emotional clichés.

Katie is married to David, who writes a newspaper column headed 'The Angriest Man in Holloway'. David is genetically cynical, gets paid to be outraged about old people on buses and dog owners in playgrounds. Her husband's reflexive loathing has, over the years, bleached all the colour from Katie's life, and she hates him for it. At one point she compiles a memorable list of all the people David has dismissed as 'talentless, overrated, or simply wankers'. It is a personal inferno that runs over two pages and includes Ted Hughes, Mark Hughes, Maggie Smith, The Smiths, all contemporary playwrights, Homer, Virgil, Coleridge, Keats, Madonna, the Pope, as well as 'anyone [David] was at school or college with who is now making a name for themselves in the fields of journalism, broadcasting or the arts'.

Like all of us, she says, she had fantasies about being a divorcee before she got engaged. All that has prevented her from going through with them has been an important sense, somewhere near the root of herself, that she should try to make things work, because, after all, she is a 'good person'.

Katie's notion of herself is threatened by the arrival into hers and David's life of GoodNews, a scrawny faith healer with an irritating line in therapyspeak. He first offers an unlikely healing-hands cure for David's backache, and then - a truly significant miracle this - draws from David's heart the miserable accretion of years of cynicism and replaces it with an unquestioning, all-embracing love of mankind.

This forces Katie to question all that she wished for. The new David is everything she believed she wanted him to be: kind, open, loving. Unfortunately he also wants to write self-help books, persuades their children to give their toys to orphans and, worst of all, wants GoodNews to move in with them.

When he does, bringing his healing hands with him, Katie is forced to address for herself the tolerances and sacrifices she might be prepared to make to improve the world, or at any rate, life within her postal district. David and GoodNews initiate a scheme to encourage everyone in the street to take a homeless person into their spare room; they make plans to eradicate world debt at the kitchen table, and, in a neat reversal, Katie finds herself cast in the role of scoffer and cynic.