When I first left the theater, I was dumbfounded. I was lost at how the director and screenwriter could have totally left out some very important parts of the story and then add things that did not exist (in the book). Granted, each movie has had some changes, however, they all fit in and were true to the story. In this case, however, the added scenes were not useful to the plot at all. Then ending was also quite anticlimatic. Those that have read the book would know there was a great battle at the end. Don't expect to see it in this film.
If the film had to stand on it's own, I would give it a B-. I think it still leaves quite a few questions unanswered. Otherwise, the read is 100 times greater than this visual.