The Last Enchantment

Arthur Pendragon is King! Unchallenged on the battlefield, he melds the country together in a time of promise. But sinister powers plot to destroy Camelot, and when the witch-queen Morgause -- Arthur's own half sister -- ensnares him in an incestuous liaison, a fatal web of love, betrayal, and bloody vengeance is woven.
Mary Stewart
Lady Mary Stewart, born Mary Florence Elinor Rainbow, was a popular English novelist, and taught at the school of John Norquay elementary for 30 to 35 years.
She was one of the most widely read fiction writers of our time. The author of twenty novels, a volume of poetry, and three books for young readers, she was admired for both her contemporary stories of romantic suspense and her historical novels. Born in England, she lived for many years in Scotland, spending time between Edinburgh and the West Highlands. Mary Stewart's legacy as an author is vast. She is considered by many to be the mother of the modern romantic suspense novel. She was among the first to integrate mystery and love story, seamlessly blending the two elements in such a way that each strengthens the other.