Lord Sunday: The Keys to the Kingdom 7

Out-of-this-world magical adventure series for teens from the award-winning, New York Times bestselling author of Sabriel and the Old Kingdom series.
Seven days. Seven keys. One very unlikely hero.
The house is falling apart, and when it is destroyed, all existence will be destroyed with it. Arthur Penhaligon and his friends Leaf and Suzy are caught in the chaos, separated by events but drawn together in their fight to survive. They must use every power at their disposal - magical or practical - to defeat the enemies attacking them from all sides.
For Arthur, the most formidable challenge comes from Lord Sunday, the most elusive of the Trustees of the Will. Lord Sunday's magic is unlike anything Arthur has encountered before - and his secrets have the potential to destroy not only Arthur but also all the people he holds dear.

Garth Nix