It's hard to tell what they're about without giving away too much info but I'll do my best. Oh BTW, it's important to know that these were written in Swedish and then translated so if you're really not into translations then they may not be for you.
Mikael Blomkvist is a reporter and co-owner of a magazine called "Millenium". They specialize in finding and exposing financial frauds. Some circumstances and a set of events led him to meet Lisbeth Salander. She's the most interesting character of the books. Following some problems as a teenager and events that are not yet explained after one and half book, she's been put under guardianship by the government. I don't know if guardianship is the right word, in french we say "Tutelle" but it's this thing where the government considers that you can't take care of yourself entirely so they appoint someone who controls your money and all.
Lisbeth is almost anorexic, she's got tattoos and piercing everywhere, she totally refuses to answer any question about herself, in short she's a complete antisocial...................but she's also a genius hacker and she's got a photographic memory.
In the first book they meet under certain circumstances as I already mentioned and they end up working together on an investigation for a very rich man who wants to know who killed his niece 30 years earlier.
In the 2nd book, Salander and Blomkvist are no longer seeing or talking to each other but somehow, and for different reasons, they end up working on the same case. "Millenium" is working on a special release of the magazine and a book about russian prostitutes that are brought to Sweden by organized crime. Lisbeth Salander also investigates this but for a completely different (and personal) reason.
