Overall, a pretty solid middle-grade novel. The concept was fascinating, but the execution a little sketchy. Mister Monday begins when young Arthur Penthaglion is at school-running. He has terrible asthma, so this is a big deal. In the middle of the attack, he sees a strange man in a wheelchair accompanied by dog-faced men with outdated (quasi-victorian) clothes. The man in the wheelchair hands Arthur a clock hand, or Key. 
 This key makes Arthur heir to the House, which is the supposed center of the universe. And this is where the idea gets out of hand . . . Through a series of events, Arthur has to enter this House, and he is dragged through an enormous amount of information and wacky characters. As might be supposed, this leaves little time for character/plot depth. Overall, it made the book feel like the insides of a clock, without a face or hands. Still, I love Nix's concepts, and Arthur is a great protagonist.