This is the first book in a series of seven. Young Arthur Penhaligon is on the verge of dying when he is unwittingly saved and dragged into a powerplay at the center of the Universe. In the highly imaginative world created by Garth Nix a Wonderland-esque House resides at the center of the universe with its various parts be ruled over by the 7 days. Each of these rulers represents a day and also seems to somewhat loosely be linked with one of the 7 cardinal sins. Mister Monday is Sloth. There is a lot of suggestive imagery and cluse dropped that enhance the adventure story that is being told.
In order to get his life back and prevent disaster visiting his loved ones Arthur must fight his way through each of the seven days and assume control of the seven areas of the house. As such the 7 books are highly connected, episodic, and I think it would be really hard to read the books out of order.
I am really enjoying this series. I'm listening to the audio and the reader is excellent. I recently read another very popular book, aimed at this age demographic (Inkheart) that I really just could not like so I'm glad to know I'm not too old to enjoy kids lit!