The Hollow Hills by Mary Stewart was published in 1973. As part of the series the Arthurian Legends, it is the sequel to The Crystal Cave. This story, in first person point-of-view from Merlin, tells the story of the birth and taking care of King Arthur. However, in this story, Merlin is Arthur's cousin, and Merlin gives Arthur to his nurse. Over time, Merlin becomes a hermit that helps others, and Arthur becomes his student. Arthur finds Caliburn, a sword, and wins a battle, where he learns his ancestry. Prior to this, he has had an affair with his sister. However, he shows Caliburn to prove his worth.
This story provides a twist to the original King Arthur and Merlin story, depicting yet another variation of the traditional tale. This particular book of the quintet series depicts Arthur's rise to fame.