Mark and Jean, an ageing media power couple, flee London for a tropical island where they continue to work  he as an advertising executive, she as a health columnist. But why is Mark receiving electronic pornography, apparently from a girl named Giovana ? Unfortunately, that question is never satisfactorily answered in this otherwise involving novel. We do, however, discover, by way of infidelity and even some disturbingly blase paedophilia, that sound marriages can survive pretty much anything and that beneath the glossy lives of successful creative types all sorts of darkness lurks. The characters are so engaging that it is easy to forgive this book for occasionally taking itself too seriously, and to forget its author is Mrs Martin Amis.

Isabel Fonseca's arresting novel begins where others end: its main characters have made their names and retired into a South Sea island sunset of afternoon cocktails, balmy air and eccentric local characters. Then Jean, a successful health journalist, opens her husband Mark's mail to find a saucy letter from a younger woman, complete with email address and riddle. Angry, confused and more than a little curious, she solves the clues and replies to the mysterious writer, and is soon staring at nudie pictures in the local internet café. When a medical check-up reveals a lump on her breast, she has even more to fear. Fonseca's novel moves from the fictional island of St Jacques to London's marketing milieu and 1970s New York as Jean and Mark's pasts return to haunt them. Her central themes - that sex does not end at 45, that the routines of marriage can hide deep fissures and that ageing makes us confront who we are - are treated with candour and colour, and this smart, clammy drama manages to be both unsettling and touching.