It's one of the biggest blockbuster collections of the century. Stieg Larsson's Millennium trilogy has sold more than 80 million copies worldwide and been made into movies in Sweden and Hollywood. The author died in 2004, at age 50, before the series took off. Fans of the iconic characters Michael Blomkvist and Lisbeth Salander thought that would be the end. But Larsson's publisher hired David Lagercrantz to write a fourth one: it's called 'The Girl in the Spider's Web'.