This series of books brings two children, Rachel and Eric, into the world of witches and wizards and magic spells. After being given power by a wizard, Rachel feels it is her duty to protect the children of the earth. These books are very good, and I would reccommend them to all ages.
P.S. Am I the only one who finds the colourful magical can-kill-you-with-one-look eyes of Rachel’s slightly disturbing?