Judith Tarr's Ars Magica is wonderful tale of a young monk in the 10th Century who learns the secrets of magic while rising in power and influence within the medieval Church. The mixture of fact (the main charecters are almost all versions of real people) and fantasy is well-developed, and the author's essay on the historical basis of her work is informative and fascinating. Fans of Tim Powers, another master of historical fantasy, may well find much to enjoy in this great novel.