Stephen suggests:
Lirael by Garth Nix
(Available here: Child Lit PR 9169.3 .N59 L57 2001)
Trickster's Choice by Tamora Pierce
(Available here: PS 3566 .I385 T75 2003)
Artemis Fowl by Eoin Colfer
(Available here: PR 6103 .O4427 A78 2001)
Tempting Fate by Esther M. Friesner