Thoughts on How to be Good-potential spoilers

I read Nick Hornby’s How to be Good a few weeks ago. After seeing High Fidelity, I read all of Hornby’s books. I enjoyed all three of them. HTBG is definitely up to the standard of the rest.
I thought the plot was inventive and handled well. The transformations the characters underwent were plausible. At first, I thought David changed too much, then Hornby included the scene with the box David saved from their wedding. I found that the most affecting scene in the book, when Katie badgers him about the box until he admits that he saved it.
The ending was more ambiguous than the endings of High Fidelity and About a Boy. I would have liked Katie to end the story happy with her family and the new David, but I think the ending is more in keeping with real life.
Has anyone else read HTBG? Thoughts?