The book is BRILLIANT, and I think that it's one of the best adaptations of a book that I have ever seen. (And yeah, James McAvoy, how can you go past James McAvoy???) Although it did make me lose faith in little thirteen-year-old children named Briony. I spent a lot of my time yelling at her from the lounge.
It's probably easier to understand once you've read the book. Just all the cutting from one time to another and all... It is confusing.