In some ways,
The Girl With the Dragon Tatoo appears to be misnamed. For much of the book, the main character is Mikael Blomkvist, a financial investigative reporter and editor of a magazine who was just convicted of libeling a major business man. Soon after he leaves his position at the small magazine he edits and that published the piece that got him into trouble, he gets an job offer from Henrik Vanger, the patriarch of a major Swedish industrial family. (And yes, the entire book is set in Sweden, which put me adrift when it came to money; how much money is 140,000 krona? Near the end there was one section which gave some help, and 140,000 krona is somewhere around $15,000 or so.) The job: to dig into the family history and find out who killed his niece 40 years ago. For about have the book, Lisbeth Salander, the title character, is only marginally involved in the story, having first been hired to investigate Blomkvist for Vanger. While the episodes involving her are interesting, they really have nothing to add to Blonkvist's investigation. But they are useful in setting up Salander's character.
The main story seems to be a rather standard one where the protagonists try to find the dastard who committed the crime, and then get threatened as they get closer to the truth. But Blomkvist and Salander make an interesting team, and Salander is a fascinating protagonist in her own right. And while Larsson does a good job in building the plot logically, the main story is obviously not the only one he is telling; after the conclusion of Blomkvist and Salander's investigation, there is still another good 50 + pages of the book remaining, as Blomkvist gets back at the business man who set him up. So, while the book is in many ways a standard thriller, when you sit back and think about it, there could very well be more there.
I have heard from somewhere that there are people claiming that Larsson is one of the best writers out there. Personally, I would not say one way or the other. Since the book was originally written in Swedish and all I've read is a translation, I can only really comment on the plotting. Any stylistic methods that Larsson used would have been at least altered in the translation; that's just the way it is.
Finally, this is apparently the first book in a trilogy, which is good, because I was kind of bummed out at the ending. Hopefully, things will eventually be tied up, one way or the other, by the end of the third book.