I'll be honest, I very rarely find films to be better than the books they adapted, and I have a theory as to why that is. With many adaptations it feels to me like one person read the book and wrote a series of bullet points on it, followed by the screenwriter reading the bullet points and writing a script that covers all of them but doesn't include any of the plot or character development that occurred between them. It would certainly explain why so many film adaptations have events occurring out of the blue instead of emerging organically from the plot and characters, and why in some cases (such as the version of "Persuasion" I saw recently) pivotal plot points are actually swapped round so that they no longer make any sense.
So the only film I could come up with for this was the Daniel Radcliffe adaptation of "The Woman in Black".
I read the book after seeing the film, and I'm not sure if it was technically better, simply because they were two very different animals. Other than the fact that the film contained a woman in black and a rocking chair, there were very few similarities between them. However, the film did include an excellent performance from Daniel Radcliffe and was genuinely scary, which I didn't feel the book was - it's rare that I'm scared by a book.
So have you seen any films that were better than the books?