Doing it with your spouse

Nicci French is a journalist who lives in London. Or so the elegant, slate-grey flysheet of her first novel tells us. Many other things have been left out of this brief biographical description, not least that French is not one but two people, and that she/they have written a very fine book. The Memory Game is first of all a murder mystery, but it is much more besides: a compelling psychological portrait of contemporary British life and a journey of self-discovery by an intelligent woman on the brink of divorce.

At the centre of the story is a sprawling family that appears, on the surface, to be both angrier and more joyous than most. The Martellos are so big they seem larded with energy. Alan Martello, the father, is a writer and a rogue. His wife, Martha, is more a mother than a matriarch. She loves her husband, but maintains her sanity by keeping her distance and holding on to her secrets as if they were lifebelts. Natalie, their daughter, is the murder victim, who died many years earlier but whose body is found just as the book opens. And Jane, her best friend, is the young woman who loves and hates the Martellos, and finally marries one of their sons, no more able to stop herself than she could stop herself breathing.

At once insider and outsider among the Martellos, Jane, the narrator, is both the book's heroine and the family's second victim. How Jane recovers the lost memories of the past, filling in the gaps, and using her new- found knowledge to save herself from the Martellos' power is the search that parallels the hunt for Natalie's murderer. Enough said. To say more would spoil the story. In any case, The Memory Game is much else besides a detective novel. It is a study in who owns truth within a family; whose truth is the truth. At the same time, it is a study in the exploration of language and what language is used for.

It was the Algerian-born French novelist Marie Cardinal who gave her best-selling autobiographical novel about the experience of psychoanalysis the title The Words to Say It. Jane also ventures into therapy to find a way forward, using language to retrieve the power she lost when she married into the Martello family. For Jane, as much as for Cardinal, reality is less about her direct experiences than about finding the words to describe what she feels. Searching her memory, filling the gaps as if mending a torn tapestry, she learns about herself and those around her. Words give Jane power over the past as well as the present.

But the most intriguing thing about this book is the fact that its clear narrative voice is the creation of two people. Nicci French - the "journalist who lives in London" - is in fact a pair of journalists, Nicci Gerrard and her husband Sean French. Their voices, when they write separately - she for the Observer and he for the New Statesman, are remarkably different, yet this was always to be a collaboration. "We always wanted to write together," says Gerrard. "And I think we found it both more and less difficult than we'd expected. Certainly, I couldn't have done it with anyone except Sean."

Each writer brought a different perspective to the project. Much of The Memory Game is set in Shropshire, near where Gerrard grew up. Her father ran a pharmaceutical business in Birmingham and her mother a little pate company called Bonne Bouche. Eldest children, as Gerrard has observed, carry all their parents' love, expectation and fear, as well as the pressure of younger siblings coming up behind.

The French brothers - Sean, Patrick and Karl - are an unusually homogenous unit. All three went to Gospel Oak school in north London. They live within a mile of each other, and still tell the same jokes. "Totally straightforward," says French, who perhaps has learned more about the intensity of sibling emotion by bringing up two of Gerrard's children from her first marriage, as well as two of their own.

While Gerrard and French found writing fiction a deux intimidating, it yielded positive rewards. The book took them only 10 months, and collaboration kept them both from slacking. "Of course, if someone else is writing you have to keep up," says Gerrard. Most of all, though, they found that collaborative writing involved what Gerrard calls "a letting go, a growing trust that goes with marital and sexual intimacy, a closeness that means you write other's imagination." That did not mean they wrote together, though. At least, not physically. "We tried it with the last chapter as a sort of grand resolution," she says. "In a way it paralysed the freedom. In fact, it was a disaster."

Instead, they collaborated intensely in the planning stages, and then wrote separately, one often picking up where the other had left off. "It's difficult now to remember who wrote what," she says. Before they sat down to write, they made elaborate plans, "sitting round the kitchen table night after night once the children had gone to bed." They sketched out four or five pages of notes on each chapter, and the same on each character, as part of the preparation.

Agreeing some details was easy. "We knew from the first that the central character would be a woman," says French. "A woman could be both assertive and a victim, and that was crucial." Other aspects were more difficult. Neither French nor Gerrard had any long personal experience of the therapeutic process, although Gerrard had sought help when her first marriage broke up and again after she spent a harrowing three months covering the Rosemary West trial. "Therapy is a bit like detection," she says. "We don't have external truths anymore, so we want internal truths. So we go down and down, and not out and out."

One of the most frightening and fascinating sections of The Memory Game is Jane Martello's growing relationship with a therapist who is clearly not good for her; excessively friendly, and open to having her visit him at home at all hours of the day and night. "It feels like a friendship, but it's really another transaction," says French. "It is a relationship that is totally open to abuse." Gerrard goes on. "It's such a dodgy area. One of the seductions of therapy is to give a voice to your suffering. People say, 'Believe me because I'm hurting.' It has such creative potency."

Both French and Gerrard found there was a lot to learn writing their first book. On balance, though, they enjoyed the experience, and have already turned in a second. If The Memory Game is anything to go by, that will also be worth looking out for.

'The Memory Game' is published next week by Heinemann at pounds 12.99