It is by the same writer of a film I have watched called We need to talk about Kevin.
The first chapter sets scene of a woman with an opportunity to kiss someone who is not their partner. There are two chapter 2s and each subsequent with different narratives reflecting different life journey from the turning point in chapter one. This takes some keeping track of as flipping between two stories with the same characters. Sometimes there are also similar events in both. A event suggesting parallel universes running alongside each other is that hose ring from a car is used as a wedding ring in one story and in the other story a car loses a hose ring.
A connection to the book for me is that my home time Sheffield features as the book includes a British snooker player and Sheffield hosts the snooker world championship.
The last chapter like the first is not duplicated. I like how the book is thought provoking about in some ways a decision can substantially alter life. The question is which life is best or will there always be good and bad bits? Ultimately fundamentally will the outcome be the same?