Please do stop me if these are becoming boring - but these books increase my understanding of films so much, I think they're great and want to collect the entire set over time. You can pick them up quite cheaply second hand on Amazon or Play.com.
This is by far the best book in this series that I have read. Not only does it open up the structure of the film to aid understanding, but the commentary is easily accessible and objectively delivered. There are many references to other films about crime and serial killers which is really useful. For me, what sets this book apart is how the author approaches and deals with sin and evil. The treatment is really enlightened and balanced - great stuff.
Look out for these small books (this one's only 88 pages) and snap them up when you see them.