This is listed on LibraryThing as Book 4 of Mary Stewart's "Arthurian Saga." The first three books are the story of Merlin as he tells it, and are a beguiling mixture of fantasy and historical fiction, with an emphasis on the historical. The first book, The Crystal Cave was assigned to me in high school. Not the usual kind of assigned reading, but I suspect my teacher was wise enough that above all, the best you can do is spark a love for reading and history, and one does not feed that on Cather in the Rye alone. (Or at all.) The Crystal Cave was the first time I encountered the idea of Arthur as historical figure, and not just of tales of magic. It had more the feel of Mary Renault's tales of ancient Greece, and I was completely enchanted by the novel and read the two sequels. Stewart is a wonderful storyteller and lyrical prose stylist.
In this fourth book we leave Merlin behind though: this book is centered on Mordred. I can't say I've read every take on Arthurian legend. (Who has? They're legion.) But I've read Arthurian novels by a lot of authors: Marion Zimmer Bradley, T.H. White, Thomas Malory, Jack Whyte, Gillian Bradshaw, Parke Godwin, Phyllis Ann Karr. And I've never seen a more sympathetic--or more memorable Mordred. I have to rate this a little lower than her Merlin Trilogy--but not by much, and that's a very high bar.
