I loved this book and was really excited to see this movie. The story is basically like a forced version of Lord Of The Flies. You don't know why this is happening to these people but its done in a way that keeps you hanging on to find out. There were parts of the book that I thought were too much or kind of silly and clearly the filmmakers agreed because they were the parts that got changed for the better in the movie. They pretty much kept to the book but with less of the drawn out fluffy stuff. It was a great paced ride with lots of action and characters that you really are able to get behind.
I would definitely recommend people checking this movie out. I can't wait to go read the other two books of the trilogy now.