It is hard for me to imagine what the experience would have been had I not read the book in the days leading up to the movie. The book obviously has more character development because you get inside the head of the main character but I felt the on-screen versions of the characters were distant and I didn't feel any emotional connection to them.
I expected a few details to be different in order to get a 2.5 hr movie out of the first book but was really disappointed and found myself asking why I should care about these characters had I not read the book and understood in more detail than the movie provided.
Hopefully the 2nd and 3rd installments will deliver more, otherwise I will consider this a failed attempt.