The new novel from the Orange Prize winning author of We Need to Talk About KevinIt all hinges on one kiss. Whether Irina McGovern does or does not lean in to a specific pair of lips in London will determine whether she stays with her disciplined, intellectual partner Lawrence or runs off with Ramsey, a hard-living snooker player.

Using a parallel universe structure, we follow Irina's life as it unfolds under the influence of two drastically different men. Lawrence is Irina's partner of nearly ten years. Ramsey is the ex-husband of a sometime friend, a once-a-year acquaintance to whom Irina has never paid a great deal of attention. Where Lawrence is supportive and devoted; Ramsey is flighty and spontaneous.

Lawrence is emotionally withdrawn to the point of repression; Ramsey is fiery and passionate, but volatile. The contrasts between the two men have ramifications for Irina's relationships with friends and family, for her career as an illustrator, and more importantly, for the texture of her daily life.

This love is about trade-offs. Both men in Irina's dual future are worthy of her affection but deeply flawed. The answer is that there is no perfect answer: one of the things that draws us to our mates is what is wrong with them. The Post-Birthday World is written with all the subtlety, perceptiveness and drama that made We Need to Talk About Kevin an international bestseller.