I've had more thoughts about this book, no doubt precipitated by the review of the Hebrew translation which appeared in yesterday's newspaper (the translation has curiously lost its definite articles, so it is now "Girl with a dragon tattoo") as well as cogitation about some of the Amazon reviews. Such reviews are torn between the desire to tell what the book is about (so that people will know whether the subject interests them) and the need to review (criticise and praise) the writing. Here I have no such problem: I don't need to tell the story and I can give as many spoilers as I want.
One person wrote about how the characters don't develop (surely, one of the tenets of fiction is that at least one character has an epiphany which changes how she feels about life and coincidentally helps her provide the story with a resolution). Another reviewer noted in response that in real life, people don't really change. Whilst that is mainly true, I know that I am trying to change, or at least deepen my understanding of what is happening around me in the hope that I will be able to impress myself more on the environment, or have the environment impress itself less on me (current book "Predictably Irrational" by Dan Arieli, which I was given as a New Year's gift yesterday). Going back to the matter at hand, Lisbeth Salander, the eponymous girl with the dragon tattoo, does change, although that doesn't seem to affect the story's resolution.
The real problem with the book is that it's really two stories in one. Now, I know that a good book has a plot and a sub-plot, but this one has two plots, neither of which is dominant to the other, and this is what caused the feeling of anti-climax at the end of one of those plots. The book could either have been about the search for Harriet Vanger, or it could have been about the shady financier Wennerstrom. The background material (whilst overly done) fits into both stories equally well. The only links between the two stories (apart from the characters) is Henrik Vanger's desire to bring Wennerstrom down, and his feeble promise about the material necessary to do so.
True, protagonist Mikael Blomkvist was lured into the Vanger plot by being promised the hot material on Wennerstrom, and his actions in the Vanger plot lead to him linking up with Salander, but otherwise the two plots have nothing to do with each other.
Ian Rankin, in his Rebus novels, usually has three or even four plots runnning in the book, but they run in parallel and are solved simultaneously by the end of the book. This has often given me a deux ex machina feeling about some of the stories; whilst I know that life - and especially police work - is not so simple, in that plots run into each other with no apparent beginning or end, and can run side by side (but not necessarily in tandem) for years, I am aware of literary constraints which demand that most (if not all) loose ends are tied by the end of the book. I often wondered what would happen if Rankin (or Peter Robinson, or any other detective novelist) would introduce a thread which does not get solved by the end of the book.
Steig Larsson has written a book with two concurrent but non-parallel plots; whilst both plots have conclusions, they are not simultaneous. So this book answers in part my query about how such a book would feel. And having read this book, I now know the answer: due to literary conventions and the escapist need to have a complete ending, I prefer Rankin with his multiple and parallel plots which finish simultaneously.