If I really have a choice I would prefer book over movies. I am someone who indulges in whatever she reads, it gives intense emotions and deeper understanding, a movie is not likely to do this. Plus, the details of the scenes provided in the book are not likely to be portrayed in a movie. Even if the director does his best to portray the details, there is no guarntee that the viewer would pay attention to everything, while in case of the book, the reader goes through everything and that's why gets the deeper effect.

Another thing is that if you read the book first and watch movie later you would be disappointed, but if you do the vice verse you won't regret.