When someone asking me those question, I would like to answer that I love both reading and watching. Even though sometimes the movie from books adaptation always gave a small different things in it, I'm still love both of it.
For example, Hobbit, have you notice the existence of Legolas? I didn't find him inside the book. That was made me more curious of what else the difference between the movie and the book. The truth there were a lot of adding scene, characters, twist and etc.
But, even though it gaves me something new, I'm still glad of it. Because I can hear the song of dwarfs. I can hear those war's song. And also I can see the goblins out from the hole. It was spectacular things I'vs got from the movie.
Because I know, it is hard, to make a movie to be completely the same as the book. And hey, I guess this is the unique side of those things! The different! It makes the story full of memories, tastes and also magics.
But when it comes to Manga, if you haven't read Manga yet, you must read it first before you watch the anime. Yes, between Manga and anime, there were the difference too, but not always. Some anime represented the story as the same as Manga. When it comes to the characters of Anime, the story becomes sooo deep. Sometimes, almost of fans can not free their mind from the male character.
Yes, almost of fantasy books already adapted into the movie yet one of my favorite book haven't heard about the adaptation of Night at Circuss book. Have you read it? I wonder who is the male character will be? Still I'm hoping the movie will be as good as the book.
I once disappointed of the movie adaptation. Have you been watching Stardust movie? I'm really hate it and then becomes hated the book too. Don't know why I had that feeling. But, it was a terrible things for me.