"The Crystal Cave" is a historical fiction novel that tells the story of Merlin, the legendary wizard of King Arthur's court. The book follows Merlin's early life, from his birth as the illegitimate son of a Welsh princess to his discovery of his magical powers and his journey to become a wise and powerful advisor to the future King Arthur. Set against the backdrop of early medieval Britain, the novel explores themes of destiny, power, and the struggle between pagan and Christian beliefs.

"The Hollow Hills" is the second book in Mary Stewart's Arthurian Saga. The story follows Merlin, the wizard, as he helps Arthur claim his rightful place as King of Britain. Merlin must navigate treacherous political alliances and supernatural forces as he guides Arthur towards his destiny. Along the way, Merlin discovers secrets about his own past and must confront his own fears and doubts. The novel is a thrilling adventure full of magic, romance, and intrigue set against the backdrop of ancient Britain.