It depends. Usually I don't read a book just because a movie is coming out. I did that for hunger games and a few other movies but that’s because my sister read the books and said I had to read them before the movie came out.
Generally I like the books better than the movies, so I like to read the books after I’ve seen the movie, otherwise I tend to greatly dislike the movie and pick it apart. And I’ll only read the book after the movie if I liked the movie, or have heard the book is better; as long as there is something interesting there.
Most times though I've read a book THEN heard it was being made into a movie. If I liked the book, I usually want to see the movies for curiosity’s sake. See if they did it justice.
So yea, that pretty complicated for me...