Superior Saturday

Superior Saturday by Garth Nix, 2008 Scholastic Books

     When Arthur returns from his grapple with Lady Friday he discovers Saturday has unleashed the human army on his hometown. With five keys in his possession Arthur is over halfway to  being an immortal Denizen of the House. He leaves Leaf in the human world to sort out his home and hurries back into the Lower House where Nothing is on the verge of destroying everything.
     Arthur goes into the Great Coal Mine where he is partially protected by the sorcery around the Old One. The Old One provides cryptic direction, but Arthur doesn't fully understand it. He makes his way into the Citadel hoping to strike at Saturday before she has a chance to summon the sorcery she has been amassing in preparation for the Will's escape and the appearance of the Rightful Heir.
     Saturday has plans to reach Sunday's realm in the Incomparable Gardens and hopes to slow the growth by destroying the Lower House with Nothing. The Will, in the form of Dame Primus, urges Arthur to return with the final two keys before there is nothing left of the Lower and Middle House. The young man, along with several old friends, travels into the Upper House where Saturday has begun her assault on the Incomparable Gardens.
     The tale ends on a cliffhanger as the battle rages between portions of the Upper House. Saturday and Sunday, their portions of the Will, and their Keys are the last obstacle between Arthur and his place as Rightful Heir. Back at home Leaf calls to Arthur as all appears lost. The story is written for middle grade readers, though those who enjoyed the preceding books will enjoy this penultimate book of the series.