How much of this is necessary?

In The Girl With The Dragon Tattoo author Steig Larsson goes into detail about the main characters' biographical histories. We learn that Mikael Blomkvist grew up in a fairly middle class stable household in contrast to Lisbeth Salander's dysfunctional upbringing. Henrik Vanger is descended from a Dutch family that settled in Sweden in the twelfth century and has a branch in America. So I ask why is it necessary to into such depth about their backgrounds? In the case of Vanger, it might be necessary only if to produce a list of suspects in the mysterious disappearance of Vanger's niece Harriet, which Blomkvist does. However, I'm not so sure about Larsson's reasons for detailing Blomkvist's or Salander's life history. Perhaps it is to provide some sort of empathy for the character or to assist any actor taking on those roles for the film version. Perhaps in later chapters we'll find out why.

As a side note I did get the kindle edition of The Thousand Autumns of jacob de Zoet, which I'll be tackling next.

Stayed tuned