P.S. I Love You is one of the rare cases where the film is actually better than the book.
There’s no depth to the characters and it’s badly written (maybe I have to blame the translation for that, I did read it in German). Where the movie made me cry about 5 times (if not more often), the book didn’t at all. The changes that were made for the film were mostly for the better (except that it plays in New York and the thing with the shoes. Though those weren’t necessarily changes for the worse).
I didn’t expect much of it in a literary sense anyway, but I thought it would be more touching, one of those mindless-but-beautiful romances. It wasn’t. The beautiful part was mostly missing.
So, I recommend everyone to watch the movie and stay away from the book. Altough it is a pretty quick read (took me two days).