I thought the book was excellent -- a real page-turner and great example of how to write a story that keeps you guessing and executes good plot twists. The only drawback was that the no-frills writing style (which I'm generally a fan of due to my abysmal concentration span) felt a bit clinical and you didn't feel much warmth for the characters. For me, the film then solved this because you were dealing with characters that you could see and develop more feeling and sympathy for.
I think this is a good manifestation of 'a picture paints a thousand words' -- great cinema can do what books can do in a much more economic fashion, and if it saves me having to read a 500-page book, that's a good thing for a lazy reader like me
