I don't generally believe in saying "the book is better" or "the film is better," because I believe that film and literature are two different media. What works in film might not work in literature, and what makes a good book might not make a good movie. When someone tells me they like the song "Venus In Furs" by the Velvet Underground, I do NOT say, "The book is better." I know some people think that films and books are easier to compare than songs are and books, but I do not.
Having said that, there are times when I enjoy one and not the other. I loved the Ghormenghast film with Jonathan Rhys-Myers, but I tried to read the book, and I could not get through it. There are times when one enhances my appreciation for the other, but this is also the case with Venus In Furs.