I can't think of a single book-to-movie where the book isn't better. Of course, I wouldn't know much, since to my memory the only books I read before they were made into a movie were LotR and those books are simply outstanding. Too much was missed out for the movies so the entire story was not told, therefore to me the books are undoubtedly better on that reasoning alone. The writing style is, of course, excellent as well.