Expert on Right Wing Extremism
One thing is for sure, Stieg Larsson wants to make sure we know everything about the central characters. Stieg Larsson was one of the leading experts on right wing extremism throughout the world and he went on to become the editor in chief of the magazine Expo (its mission was to expose the right wing extremism). He also worked as a consultant for Scotland Yard, which means he was just the right person to write the Millennium trilogy.
A Society Built With Characters
The book is replete with numerous characters, and there is quite a society built within the books. The social structure is pretty much evident through the way Lisbeth Salander is hired by Henrik Vanger (you'll come to know about the complicated route when you actually read the book). Stieg Larsson believes this is how the world actually works and Larsson makes sure this is an integral part of his social commentary.
It's a Personal Quest for Blomkvist, Too
The event when Blomkvist was jailed due to the charges brought by the corrupt Wennerstrom and his (Blomkvist's) quest for revenge is central part of the theme, which runs throughout the book. Even the peripheral characters are no less important in the book (even the daughter Mikael Blomkvist helps with the Bible references). Everyone in his book wants to control the others throughout in the series, including Erica Berger, the protagonist's best friend and boss, who is a powerful woman who controls all aspects of her own life and the men around her. Mikael Blomkvist's life is being controlled by Henrik Vanger who promises handsome financial and professional rewards if he gives one year of his life to Vanger (to investigate one past family incident).