I think there was another similar topic some time ago (Books to movies: http://bookclubforum.co.uk/forum/showthread.php?t=5093).
From which I quote myself :
"the point is that ther's no way you can (magically) turn a book into a film. the film will always be...another thing. each has its own peculiar way of being, of dealing with the spectator/reader. they shouldn't be compared as if they belonged to the same category. they don't anyway. the time allotted for each of them is different, the way a film can use lyrics to convey a message which is hidden or implicit in the book. the only point which is shared is the underlying facts, not even the story, because often this is bent to please the viewers. I don't say you can't appreciate a film which is based on a book, I only say go to the theather without expecting to feel what you felt reading, because this will never happen."