Ugh, this was disappointing. I felt like I was reading the author's character sketches for a book, not a finished novel. Lively gives us many points of view to her central story, which apparently took place fifteen years in the book's past. But each character is a flat, one-dimensional type who fails to do or reveal anything interesting or surprising. And, except for the dead woman, they are all tedious people, which is my very charitable explanation for the terrible prose in which this book is written.
The story is that the main character, a dry, ageing academic named Glyn, discovers a photograph which reveals that his now-dead wife had an affair with another man before she died. It's clear from how the characters avoid discussing her death directly that she died either by murder or by suicide, and we can rule out murder because there's no intrigue about it. So Glyn goes on what the book describes as an obsessive quest (but it feels more like academic research) to find out if his wife had other affairs. In the process, he learns that he didn't know her very well and that she was unhappy. His quest doesn't change him, just as none of the other characters learns anything from being dragged into his research project with him. Then the book ends with anticlimactic revelations about how the characters each experienced the dead wife's last day and *gasp* we find out that she did indeed commit suicide. Glyn decides that he "has to find a new way of living with Kath, or rather a new way of living with a new Kath." But as a reader, I was left with serious doubts about whether Glyn was going to find a new way of doing anything, ever.