Lord Sunday is the seventh book concluding Garth Nix's The Keys to the Kingdom series. The book was released on February 1st, 2010 (Australia). The description reads "Arthur Penhaligon must complete his quest to save the Kingdom he is heir to... and Arthur's world." The book was the number 14 top selling book in Australia during its launch week. The book was released in Australia on February 1, 2010, the U.K. on March 4, 2010, and the U.S. on March 16, 2010.