April Books 15) The Lives of Christopher Chant, by Diana Wynne Jones
I think this is my favourite of the Chrestomanci novels, a prequel with some retracing the steps of Charmed Life, but adding some extra wrinkles which I found more satisfying - the parental marriage disintegrating; the young goddess of cats; the boarding school; the interdimensional smuggling racket; and the answer to the question of what happened to Chrestomanci's other lives. Young Christopher's psychological alienation, temptation, and eventual redemption are a very effective story arc. Even though we see even less of the world of Chrestomanci here than we did in Charmed Life, it still feels like a rich and intriguing environment. Like all of the Chrestomanci books it reads perfectly well as a standalone, with no knowledge of the rest of the series necessary to enjoy it.