Sir Thursday, the next volume in Garth Nix's "The Keys to the Kingdom" series, will be published worldwide in early March 2006. On Amazon, the paperback has a current sales ranking of 137 in the UK, and the hardback a ranking of 437 in the US. Very respectable numbers indeed.
In the lead-up to publication, you can play an online game based on the series at the Scholastic website. You can also read the prologue to the novel on Garth's website.
[Thanks to Liz at A Chair, a Fireplace and a Tea Cozy for the game link.]