The Mystery of Mercy Close, By Marian Keyes

Who are you calling a chick-lit heroine?

Marian Keyes's debut, Watermelon, burst upon the scene in 1995, topping the paperback charts and jump-starting the pulse of a nascent genre. Seventeen years and a dozen Keyes titles later, the pundits have announced the demise of "chick lit", yet her books continue to be international bestsellers, as do those of Lisa Jewell, Jenny Colgan and other favourites who have been bracketed within the trend. Good writers move with the times. Their characters have other interests than finding Mr Right, and the heroine of this novel swigs Diet Coke instead of Chardonnay.

In Watermelon we first encountered the dysfunctional Walsh family from Dublin: soap-watching Mammy, her bemused husband and their five rampant daughters. Four of the girls have starred in their own novels, and devotees will be delighted finally to read about the youngest, Helen, in The Mystery of Mercy Close.

The petite man-eating twenty-something we glimpsed in Watermelon and Rachel's Holiday is now an edgy misfit in her thirties. And if the book title suggests suspense, it's because Helen has set up as a private investigator, having been fired from every job she's ever had. Times are hard, however, and Helen is forced to accept an assignment from her charming but unreliable ex, Jay Parker, now the manager of a washed-up boy band. One of the members, Wayne, has disappeared days before some game-changing reunion gigs and Helen's job is to find him in time. At least the case will pay a few bills and divert her from fretting about her gorgeous boyfriend Artie, whose ex-wife and kids claim his attention.

Helen is far from the de rigeur sympathetic heroine of so-called chick lit: she dislikes children and animals and always speaks her thoughts, which are usually scathing. Keyes's use of the confessional voice and a beyond-black humour beguile the reader into empathy, which is all that's required. I didn't find the missing-person investigation itself compelling, but Helen's picaresque path to redemption is. She's gut-bustingly funny. While she trawls answerphone messages, searches Wayne's house for clues and interviews the other band members, she sends up tawdry celebrity culture, rants about contemporary lifestyles, and continually updates her Shovel List. This last is an excellent survival tool for modern life: "A list of all the people and things I hate so much that I want to hit them in a face with a shovel."

Beneath the warmth and the zippy dialogue sounds a note of vulnerability, and it's this that gives Keyes's writing its special appeal. Her women are whistling in the dark. They're never earnest. They don't want to complain or to bore the reader with their problems, but one senses all too clearly that they're in pain. It's no surprise to learn that their creator knows whereof she speaks. Helen is visited by bouts of clinical depression and while she makes light of it all, dark undercurrents are aswirl.

Alas, there are no more Walsh sisters after this, but for aficionados there's an ebook coming called Mammy Walsh's A-Z of the Walsh Family. This reader can't wait!

Rachel Hore's novel A Gathering Storm is published by Simon & Schuster