The Keys to the Kingdom. Book One. Mister Monday

Seven days. Seven keys. Seven virtues. Seven sins. One mysterious house is the doorway to a very mysterious world -- where one boy is about to venture and unlock a number of fantastical secrets.
This is another thrilling, triumphantly imaginative series from Garth Nix, the best-selling author of The Seventh Tower, Sabriel, Lirael, Frogkisser!, and the Troubletwisters series.