So I downloaded it and loved it! It's funny and moving. The novel spans a couple of decades and each chapter takes place on the same day, usually a year or so apart. It is a chronicle of a friendship between Dexter and Emma and the first day we meet them is on the day of their college graduation when the "hook up," as we say today.
Over the course of the next twenty years we catch up with them as they reconnect and bicker and eventually end up together. Dexter is a mess throughout, until he finally gets with Emma, who stabilizes him.
I think I will look for other David Nicholls books. I think that there is a brand new one out now!