IN TESSA HADLEY's new novel, she writes about early mid-life crisis. What it's like to sleep with someone less than half your age.

How it feels to abandon your children for a weekend of camping, drinking and smoking marijuana.

Why all of a sudden, people crave a life completely opposite to the one they're living. In The Master Bedroom, Hadley's characters know they're acting irresponsibly, but can't stop themselves.

The story is set in Cardiff and intertwines two families: the Flynns and the Robertses. Kate Flynn takes a year out from her job as a university lecturer to look after her elderly mother at the family's grandiose home, Firenze.

On hand to support Kate is her old college friend Carol, whose younger brother David is experiencing marital difficulties with his wife, Suzie. David starts hanging around Firenze while Suzie is out camping with her friends, a new-age couple that David dislikes.

A web of relationships is created, each involving Kate: a polite, platonic one with David; a struggling, passionate one with his son Jamie; a sisterly one with Suzie, who confesses to Kate that when a dead swan fell on her car, she thought the message was:

"Make a mess out of everything you've got."

Hadley's writing is fluent and tightly controlled, her closing sentences like perfect cadences.

She has an ear for music, and classical works play a large part in the novel. The pieces seem carefully selected to convey mood.

As ever, Hadley's powers of observation hone in on certain aspects of human existence. Sex, as Hadley describes it, is an escape from all formality. Violence too, is part of being human, noted when David and Suzie engage in a vicious physical scuffle. Suzie suffers from paranoia when she imagines it was Francesca falling from the sky and not the swan.

Hadley is also skilled at conveying the smallest anxieties: David checks his watch in the park, worried that the gates will close on him; Kate clutches towels on the lake shore, wondering what she'll say to David if Suzie drowns.

The style is in fact more engaging than the plot. Beautifully measured prose overshadows these timid characters. At the novel's close, they all give up and avoid confrontation, which is disappointing.

There is no father-son bust up between David and Jamie, no hard words between Kate and Suzie.

Instead the characters return to their routine lives in the suburbs as if nothing happened, or it happened in another life.

The later stages of the book, in fact, read like scenes from a movie.

Kate wanders home through the park, revelling in Cardiff 's wintry beauty: the large white sky, the gigantic beech trees. And in the end, a particularly affecting finish shows that style can indeed triumph over substance.