Sir Thursday by Garth Nix is the fourth book in the Keys to the Kingdom series.   Arthur is intent on heading out of the House and returning to the secondary realms to check on his family before he tries to find the next part of the Will and win the next Key.  But that is not to be.  Instead he is unable to return to his home because someone else is already there, pretending to be him.  Luckily, his friend Leaf can return and do battle with the strange creation that is impersonating him.  While he is trapped in the House, Arthur is drafted into the Glorious Army of the Architect under the command of Sir Thursday.  Arthur has to survive not only basic training, but a suicide run led by Sir Thursday himself. 

If all of this sounds a little confusing, that is part of the charm of this series.  The books are set in the House where the Universe is run.  Arthur is a reluctant hero who has been chosen as the Rightful Heir.  Because his own world and his family are threatened, he is forced to continue to battle through the Morrow Days one by one, putting the Will back together and gathering the Keys.  To my great joy, Arthur is accompanied now by two great girls who face battles themselves: Leaf and Suzy Blue.  The child characters are vividly rendered and they are surrounded by complex characters in the House.  The entire series should be read from the first, Mister Monday on through.  No skipping around, or you will miss some of the fun!

This book is recommended primarily for those who have read the first three.  But it could serve as a way for new people to get hooked on the series, wondering what they have missed.  It is not for reluctant readers or squeamish ones.  This is a dark series filled with humor and action.
Released March 2006.