This is the first book in Garth Nix's Keys To The Kingdom series. If you enjoy fantasy fiction like Harry Potter, or Eoin Colfer's Artemis Fowl books, then this series is for you. I have read most of Garth Nix's other work and these books are my favorite of his to date (2009). The tone of these stories is far less dark and creepy than most of his other ones (which I liked too), but the world and the storyline he has created here just feels more fleshed out and complete.
He draws on elements of Christian religious tradition to frame his story, but in ways that are quirky, almost absurd, and not really corresponding to any kind of religious orthodoxy. It is chock full of interesting ideas though, and great fun for adults who might "catch" more of that as they read than a kid would. It has been pointed out that the characters the books are named after (unfaithful "Trustees" who are supposed to uphold the Will of the Architect/Creator who has vanished and left the Universe and all creation in their hands) correspond to the seven deadly sins in the manner in which they each are corrupted and fail in their duty. These being sloth, pride, gluttony, et al.
The hero of the piece, Arthur Penhaligon, is a young, teen-aged boy who by chance and against his will finds himself charged with defeating each faithless Trustee and setting the "universe" to rights. He feels impelled to do this because it is the only way to protect his own world, his family and everything he cares about, but the process makes him less and less human and possibly unable to ever return to his normal life and existence.
Garth Nix is one of my favorite authors and this series is some of his best work ever. I highly recommend it.
The complete series is:
Mister Monday (book 1)
Grim Tuesday (book 2)
Drowned Wednesday (book 3)
Sir Thursday (book 4)
Lady Friday (book 5)
Superior Saturday (book 6)
Lord Sunday (book 7, not yet released as of this writing - May 2009)