Just watched it last Sunday, and I think David Fincher did a great job adapting the novel onto the large screen.
I’ve read the novel two weeks ago (If you have followed my blog you should know that, but I know you didn’t). The novel itself is good, focusing in details and never lack of twists. But to someone who had watched tons of movie/TV drama that are full of blood / gun / blade / and body parts, it is just OK. However, the movie tighten the loose part, delete the unnecessary characters and even change the original story, and everything just make sense and exciting!
If you haven’t watched the movie yet, I would recommend you go and give it a shot. There’s no need to read the novel first. However, if you do want to read the original, I would assume you will feel the same way as I did.