PSYCHOLOGICAL thrillers don't come much better than those of JP Delaney – and this fourth novel is even better than last year's The Perfect wife.

The author really knows how to get an emotional, physical reaction from the reader – from a sinking feeling in your stomach or a growing sense of trepidation, to the sucker punch of an unexpected twist.

You won't necessarily love the characters in his novels – they all come with secrets, baggage and flaws – but you'll certainly care what happens to them as you desperately turn the pages to finish the book in one sitting.

Delaney takes a high-concept and wrings every possible plot development out of it, making everything credible due to the strength of her characterisation.

In Playing Nice the concept doesn't have the sci-fi element of The Perfect Wife: this time it's something that could happen to anyone, the accidental swapping of two babies in the delivery room.

All-round nice guy Pete and partner Maddie don't find out until a couple of years later when another father, Miles, rocks up on the doorstep to say their son Theo actually belongs to him.

Miles and wife Lucy have been unknowingly raising Pete and Maddie's son David, who has severe learning disabilities due to birth complications.

The relationship between the four parents is initially cordial: they try to make the best of an unusual situation and try to play a part in each other's lives so they can do the best for both children.

But all four of the adults have secrets, not all of them are totally sane, and at least one of them has an ulterior motive.

It's no surprise that increasing complications see the couple end up in family court, that they set lawyers on to the hospital, or that the police become involved.

But that's only halfway through this novel: there's more, far more, to come.

An intriguing set-up, a plot that propels the novel forward, a gradual tightening of tension, and a hugely satisfying final third. There's nothing nice about this story.

* Published on August 6.

David Knights