1970 novel by Mary Stewart. New York, Fawcett Crest. ISBN 0-449-20644-0
An engrossing and well-written retelling of the Arthurian legend (see Arthurian Mythology and The Chronicles of King Arthur for lots more on this topic), from the birth of the magician Merlin (Myrddin) to the conception of King Arthur. Narrated by Merlin from the title location, which has been important to him throughout his life and which is his prison as an old man.
The Arthurian myth is a great one, chock-full of magic, politics, and other intrigue, and Stewart's version does it all kinds of justice. She casts Merlin as the bastard son of a Welsh king whose daughter steadfastly refuses to name the father of her son, to the point where rumor has it he was sired by a demon. When Merlin learns of his father's identity, the reasons for her secrecy are all too apparent, but she sticks to the demon story when the Saxon-allied King Vortigern of England, advised by his wizards, tries to claim the apparently fatherless Merlin as a human sacrifice. The latter defies the court magicians and proves himself a prophet in his own right, paving the way for the exiled Ambrosius Aurelius to reclaim the kingdom Vortigern took by treachery years ago. Ambrosius' brother, Uther Pendragon, later becomes king and fathers Arthur Pendragon with Merlin's help.
The author provides a summary of the story that supplied the basic plot of The Crystal Cave, as well as references to various sources, historical and literary, which informed her writing. Subsequent books in Stewart's Merlin Trilogy: The Hollow Hills and The Last Enchantment, as well as a fourth book, The Wicked Day, told from Mordred's point of view, complete the telling of the myth through the collapse of Camelot.