It is a very enjoyable movie, and for practical purposes I do understand it just wouldn't be possible to make a movie including the entire book (guestimating based on the time of this movie with what was included, I'd say an unabridged movie would easily be 8 hours long).
I did find the things that were not included in the movie and the subtle rewrite of the story to handle those missing parts jarring. I was looking forward to seeing scenes from the book which were excluded from the movie, and that was my only real problem.
I won't give any spoilers, but I am highly tempted to talk about a major part of the book that was totally omitted from the story. Since that is a kind of spoiler too, I won't say what's missing.