Similarities and differences on book-based movies

There are a lot of movies that there are based in books, some of them are famous, others not at all. I think that some of those movies are complete different of the books, so we don’t have to be expecting and plenty of hope because we could be a little disappointed. Some time, the movies are like a different world, with different names of characters and other kind of events, even though a different final of the movie. So I think that it is complete necessary to read the book first to be a critic opinion of the movie, and if we want to enjoy and laugh about the adaptation we can go to the cinema but, take it easy, it is only an adaptation, it is not the book. But I thing that there are good book adaption´s movies that we will be satisfied, like The Lord of the Ring, because the book was the fundamental base for the director to creates and imagines the movie. The book was important for the esthetic, for example, the landscape, the native language that the characters speak in same scenes. Now, I think it is impossible to read the book without an image of the movie. I think that some kind of these movies has been received in a good way but others, the most are very hard criticized, depend of course of the audience.