The preview for the US version seemed to explain the story pretty well, which is what spurned my interest. I'll give the book a try as well, though I tend to only half read books
If you are going to watch the original Swedish version, be prepared. It cuts out quite a bit of the story. There is just so much information in the books that it's impossible to get it all in there. But I love the Swedish movies and I'm excited (but hesitant) for the US version.