I know what it is like when you read a book. You get a really specific idea in your head on what it's going to be like. Everyone's ideas are going to be different, there's absolutely no way that it's ever going to match your imagination and it's so hard to let that go. Once you see the film, you see the characters as the actors. It's always hard at first to make that transition and let the actor kinda take on your character that's playing in your head... you just have to be open-minded and ready for something new.
