The Wall Street Journal has some emails from Stieg Larsson, author of The Girl With the Dragon Tattoo and following popular crime novels. The author writes of his intention to work around the usual formalities of crime novels. Main characters are not from typical crime novel stock, and he didn’t want his serial killer offing anonymous people, so he spend time introducing minor characters. In real life, no one is completely anonymous. He also states:

A rule of thumb has been never to romanticize crime and criminals, nor to stereotype victims of crime. I base my serial murderer in book I on a composite of three authentic cases. Everything described in the book can be found in actual police investigations.
The description of the rape of Lisbeth Salander is based on an incident that actually took place in the Östermalm district of Stockholm three years ago. And so on.

Lars reviewed The Girl With the Dragon Tattoo here, and the following book, The Girl Who Played With Fire in this post.