I'm not going to sit quiet while someone insults one of the greatest series of fiction books ever written. The Chronicles of Narnia are about Christ. If you want to deny that, read CS Lewis' letters of correspondence with children, in which he states that Aslan is Jesus the Christ. Also, CS Lewis called Christianity the "True Myth." By the way that phrase is not a post modern new age phrase, but in fact is derived from the very foundations of Christianity in the Middle Ages, in which the word "myth" meant an explanation for unknowable things. The story of Christ is the "True Myth" because it explains unknowable things, and is true.
Why is there magic in Narnia? Because its a children's story. Many children's stories are filled with magic. Magic is not witchcraft or sorcery outright. Case in point, the Saga of Middle Earth. Gandalf the Wizard, is not a wizard at all, but is in fact an angel given mortal form, sent to this world to contend against a fallen angel known as Sauron. What Gandalf does is the power of God working through him, what Sauron does is sorcery (or using the laws of the universe for selfish devices).