Movies based on books are never as good as the book. I have to watch the movie first and then read the book, if I do it the other way around then when I watch the movie I start thinking about how it didn't happen that way, or that the character had black hair and the actor has blonde, etc...
Although, I don't think I'll read Divergent. The movie was really intense, so that's a signal to me that the book will probably be the same way. I can handle an intense movie, but intense books are just a whole other level, and I tend to like a slightly more "sedate" story. I'm a strange person.