I have a bit of dilemma, whenever I know that a film is actually a novel, I like to read the novel first, but then when I watch the movie after I've read the novel, I find it horrible because I've already engaged my imagination in the detailed version.
On the other hand when I watch the movie then read the novel, I become uneasy because I already know the ending.
On a different, but not so distant note, I really recommend "Horton hears a who"; being a great fan of Dr. Seuss and cartoon movies.
"I meant what I said and I said what I meant
An elephant's faithful 100 percent"
I don't however recommend "PS I love you", because the movie is absolutely boring and not worth your money. The only good thing about it is Ireland and there isn't that much of it to sustain you through an otherwise excruciating movie.