I saw this recently at the cinema. I loved it! I had not been able to read the book from cover-to-end, mainly because I found it difficult going. The film, on the other hand, was totally digestible and most enjoyable.
My favourite character, is Marvin, voiced by Alan Rickman. His voice is sufficiently depressive enough to be funny.
Die hard fans will disagree, but I much prefer the movie to the book.