Usually, more people tend to like the book better than the movie. Movies, most of the time change scenes from the books. I get mad when a movie changes something from the book. Some people feel disappointed in movies after reading the book first.
Sometimes people read books before they see the movie. If the movie is really good and people hear others talking about it, they get pulled into reading the book from the movie. Some people decide to read the book to a movie that has become really popular, before watching the movie. I feel like I have to rad a book before I watch the movie, because I like knowing what will happen in the movie. I also feel, that if you read a book before the movie, the book will provide you with more information. Therefore if you miss something in the movie, you know why it happens.