Agatha Christie: an English mystery, By Laura Thompson

Mysterious affairs re-styled

Who cares who killed Roger Ackroyd?" asked the critic Edmund Wilson in 1944. Yet somehow it is Wilson himself who is outdated in the postmodern literary world, where narrative has returned and the power of plot is once more acknowledged. Agatha Christie's The Murder of Roger Ackroyd (1926) now seems a very modern text, with a narrator of positively Barthesian unreliability. Poirot can be accepted as an enabling device, with no anguished search for depth of character.

Christie's references to drug addiction among ex-soldiers, and to a sharp divide between wealth and poverty, have contemporary resonances, and many commentators would agree with Francis Wyndham that her books can be viewed as a form of animated algebra. This and other critical comments are included in Laura Thompson's detailed biography, which also uses many excerpts from Christie's own writings to fill gaps in the hidden inner life of her subject.

Thompson is to be congratulated in delving deeply into the lesser-known romances written under the pseudonym of Mary Westmacott, as well as into the better-known adventures of Poirot and Marple, but the result tends to be a somewhat gushing style and a flaky biographical technique which lapses into inner musings.

It is inevitable that we should look for secrets in the life of a mystery writer, but this quintessential bourgeoise seems deliberately to have provided us with a real-life thriller. Thompson rehashes the curious issues surrounding the celebrated "Eleven Missing Days" of 1926, when the author vanished from her home in Sunningdale. Because her car was discovered perched on the edge of a quarry on the North Downs, there were fears for her safety, but she was eventually discovered staying in a Harrogate hotel, where she had assumed the name of her first husband's mistress. Her own explanation was amnesia.

The incident provides a test case for her biographers. Those who have had the imprimatur of the Christie family and been granted access to the family papers, such as Janet Morgan, have been very charitable towards the writer. But Jared Cade, treated in very hostile fashion by Christie's family, and now by Thompson, looked elsewhere. He came to the conclusion that the episode was deliberately plotted to punish her erring husband. Cade presented a considerable degree of proof, not successfully vitiated by Thompson's Poirot-like delvings into rail timetables.

There are other aspects of this book which betray censoring influences, such as the relationship between Agatha and her second husband, the eminent archaeologist Max Mallowan. It has been an article of faith that this marriage was blissfully happy, whereas there is ample evidence that Mallowan was carrying on an affair for many years with his scholarly assistant Barbara Parker, eventually his second wife. When I met the second Lady Mallowan, an extremely elegant and attractive woman even in old age, I thought it inconceivable that Agatha could have been in utter ignorance.

Mallowan appears to have treated both women very shabbily, but Thompson clings to a more seemly version. Agatha may have chosen to shut her eyes, but a biographer's duty is surely to be more realistic.

Thompson has much sympathy for Christie's battles with the taxman, yet much of the Byzantine fiscal entanglement was caused by canny schemes to protect the author and her heirs. She was turned into a limited company which paid her a wage (very modest – £5,000 in 1958), and a trust was formed to handle her copyrights. Thompson says melodramatically that "the fact that she left only £106,600 was in fact no mystery at all. Everything else had been taken from her." That's one way of describing extensive tax avoidance. Once again, objectivity is lacking from this account.

The book raises an important question for biographers: is generous access to archives worth sacrificing independence for? There is a vast amount of early detail here, which may fascinate buffs, but much is of the bus-ticket variety. There are lengthy accounts of Christie's parents and grandparents and her unexceptional early life, but Thompson has preferred to overlook a painful recurrent theme: that Christie had a pattern of attachments to dodgy men.

This included not only her adored father and her two husbands, but the Egyptologist Stephen Glanville, well-known as a philanderer, with whom she had a hothouse relationship. Betrayal and jealousy were vital ingredients in the world of Agatha Christie: she sought them out in real life and made use of them in her fiction. That makes her a much more interesting subject than Thompson's bland approach would allow.

Jane Jakeman's 'In the Kingdom of Mists' is published by Black Swan