Stieg Larsson died of a heart attack in 2004 – after he'd delivered the finished trilogy to his Swedish publisher Norstedts, but before his work was published (source).
If you go to Sweden, you can take a tour that will show you the Stockholm of Blomkvist and Salander, even their apartments! If you can't go to Sweden, perhaps this virtual tour will give you some satisfaction.
Astrid Lindgren, whose characters Pippi Longstocking and Kalle Blomkvist inspired Salander and Blomkvist, died in 2002, right when Stieg Larsson was writing the trilogy (source).
Eva Gabrielsson, Larsson's live-in partner of over thirty years, is in possession of a partial draft of the fourth installment of the Salander-Blomkvist novels (he planned for as many as nine or ten) and Larsson's computer, papers, and notes. Since Larsson's father and brother have the rights to the proceeds of Larsson's work (since Larsson and Eva never got married), Gabrielsson isn't currently planning to release the material (source).
Gabrielsson says, "when [Larsson] was 14 or 15, he was witness to a gang-rape committed by his so-called friends. This is the key thing. For him, the fight against violence against women was personal" (source).