The important thing to keep in mind is that books and movies are two seperate mediums, and never the two shall meet. (Well, successfully, anyway)
There is not a single book -> movie adapdation ANYWHERE that does not have detractors.
If you could just watch the movie as if it had nothing at all to do with the book, I think people would find a lot less flaws. I don't know why 'purists' go to the movie wanting to see the book on the screen. Doesn't that defeat the whole purpose of reading the book? Was something wrong with the book? Was your imagination not functioning enough for it to be a compelling adventure on its own?
If all of that's true...don't nitpick the film based on how well it does (or does not) 'follow the book'. They aren't the same thing at all. One is on paper, and comes alive in your mind. The other is on celluloid and comes alive with surround sound on a movie screen. Given even perfect book->movie translation; a scene-by-scene, line-by-line, 17 hour extravaganza....they STILL wouldn't be the same.
So, go home, read the books, and ENJOY them. And watch the movie, and ENJOY it, too - but for DIFFERENT REASONS.