Tamora Pierce's books seem to be suitable for that age. I recommend starting with The Song of the Lioness quartet. The first book is Alanna: The First Adventure.
ETA: Oops, looks like BaenSidhe already beat me to it haha. Shame on me for not reading all the responses first. Pierce has 2 universes she writes about. The specific books BaenSidhe and I suggested are of opposite universes.
Last edited by odiakkoh; 03-22-2013 at 04:14 AM.