Charmed Life

After the parents of Gwendolen and Cat are killed in an accident, the siblings go to live with the world's most powerful enchanter, Chrestomanci, in the hopes that Gwendolen, the only one of the two with magical abilities (or so it is thought) can be tutored by the enchanter. Gwendolen becomes angry after Chrestomanci fails to make much of her magical abilities and disappears, only to be replaced by a decidedly nonmagical duplicate, Janet.

The story is great fun, with a big alternative world where magic is commonplace as the setting, and the characters are wildly original, including the calm and cool enchanter and the easily angered Gwendolyn. I delighted in the twists and turns of the plot as well.