Books to Movies Good idea or not??

With the release of the latest Twilight movie it makes me think of how good a job they really do making a book into a movie. I enjoyed Twilight and I happen to really enjoy the books in the series. With the first movie I read the book after seeing the movie, and then when I watched the movie again I was disappointed a little. I am hoping that it is not the same with this case but I fear it will be. I find Hollywood remakes of books very often disappointing. I understand you can't get all the details of a book into the movie however I do not see the need to change the story completely. In many cases such as My Sisters Keeper or The Notebook they change the ending completely. After hearing about the changes in My Sisters Keeper I am not willing to watch the movie yet, that may change in the future but I doubt it. As for The Notebook most people I know love the movie, however after reading a sequel to the book I can't like a movie that has someone die who is in the sequel. If you want to make a movie version of a book and you drastically change the story you are defeating the purpose. I get they sensationalize aspects and want to add interest but I don't like it. In the case of The Lovely Bones which is now a motion picture I enjoyed the book so much I am afraid to see the movie in case it is yet another bad job. Maybe it is because I enjoy reading so much but movie versions are such a disappointment to me.