A simple fact of life is that there will never be a movie that everyone loves. There will always be people who find something to complain about or simply find that for whatever reason that movie is just not for them. While it is often exciting to see a book turned into a movie, the filmmakers are contending not only with the challenge of making a good movie that will please critics and film goers, but they are also trying to please a preexisting fan base who don't want to see anything happen to their beloved story. Unfortunately this is an impossible task because as I said before every reader has their own idea of what the world and the characters are like.
Another unfortunate reality about book to film adaptations is that there will always be thing that are omitted or changed during the transition from page to screen. Again readers always have their favorite scenes or things that they believe are essential for the story, and sadly sometimes they don't make it into the film or are changed to fit the adaptation. The reason for this is simply because authors have room to play with that directors and screen writers do not, otherwise book to movie adaptations would be ridiculously long and wouldn't be feasible to make or watch. That being said, changing a story for film has to be done carefully so the plot still makes sense.
In the last few years book to movie adaptations have become more common and often they don't seem to do very well. The case usually seems to be that book adaptations are either received well by the fans, or by the critics, but is very rare to see them accepted by both groups. I think this is usually because the story is either changed so drastically that fans don't like it, or the story follows the book and people who haven't read it get confused. In the end making a good movie out of a book is very difficult because it has to be a good movie on its own as well as true enough to the original story that the fans still want to see it.
In the end the most important thing to remember about book to movie adaptations is that the movie is not the book! It is an interpretation of the story done by a few people who are attempting to please as many people as possible. The movie will never make everyone happy and there will undoubtedly be things that are changed in order to make the movie make sense for those who have not read the book.
My final advise; if your favorite book is turned into a movie go see it! Remember it is an adaptation of the book and not the book itself. If you enjoy the movie then it doesn't matter if other people don't like it, be happy about the fact that you will be able to see your favorite story come to life whenever you want to. And if you don't enjoy the movie then simply go read the book again!
