The Girl With the Dragon Tatoo is a murder mystery that is set in Sweden and deals with some serious psychopaths similar to the movie 7. I cannot say that I would recommend this book necessarily. It is a little too dark, and not well written enough, and there is no real substance, theme or message to it. It is, in a word, a kind of pulp. Maybe a good book to pass a voyage or plane ride, where you don't want to think much, but that is all.
I actually enjoyed the 2 books. Forgettable as you said, but utterly entertaining in a straight-forward way.