The fourth novel will be written by Swedish author David Lagercrantz, who is not exactly a household name in Sweden, but has co-authored an autobiography of a Swedish "footballer" and has written some fiction. He was apparently chosen by Quercus because he "has in his writing constantly sought out odd characters and complex geniuses".
I'm always dubious about one writer taking over another author's works, although it's a fairly common practice (for example, Felix Francis for his father Dick Francis, Andrew Neiderman for V.C. Andrews, and various writers for Robert Ludlum). On the one hand, this practice encourages continued interest in the original author, who may have died prematurely, and allows his/her fans to enjoy a similar type of novel. On the other hand, the practice can be viewed more cynically as a means of generating ongoing revenue for the publisher.
In any event, it will be interesting to see how the uniquely individual Lisbeth Salander fares in the hands of a new author.
For the full text of the article in The Bookseller, please click here.
On another note, I'd like to wish you and yours a safe and happy holiday. Merry Christmas!