The Keys to the Kingdom
The Keys to the Kingdom is a fantasy–adventure book series written by Garth Nix, comprising seven books published between 2003 and 2010. The series chronicles the adventures of a boy named Arthur, who becomes involved with a magical world called the 'House'; he is on a quest to take back the House from seven antagonistic 'Trustees'. Source: Wikipedia (en)
Series - wd:Q1540209