Lionel Shriver's The Post-Birthday World is the Oxford Mail Book Club's current novel - on offer at Waterstone's in Oxford and Witney with the voucher printed in tomorrow's Oxford Mail.

It's an engaging, post-modern novel from the author of We Need to Talk About Kevin. And despite her name, Lionel's a she.

The story is told in the third person, from the point of view of American children's book illustrator Irina McGovern, who lives in London.

She is happy enough with boyfriend Lawrence Trainer, who works at a prestigious think-tank but the thrill she felt when they first met has long gone.

Then she meets hard-living top snooker player Ramsey Acton, is drawn to him, and the feeling is mutual.

Lionel Shriver then tears up the rule book by setting up a parallel universe structure, allowing the reader to follow Irina's competing futures with two drastically different men.

In the new paperback edition of The Post-Birthday World, published by HarperCollins, Shriver explains why she decided to split the narrative, and insists that the purpose of the unusual structure is not simply to play literary games.