The Hollow Hills by Mary Stewart (1996, Paperback, Reissue)

This is the second in a series of three books that uses Arthurian Legend to tell the life story of Merlin. Merlin is known as: The Enchanter, The Prophet, Magician, Advisor to Kings, a mythical figure of King Arthur's time. This book picks right up where the first book, The Crystal Cave, leaves off. It tells of Merlin’s life from just before Arthur’s birth, until the famous Sword incident that demonstrates that Arthur is the right choice to be King of all England. Merlin's part in the overall Arthurian story is told in this book along with the other two books of this series, The Crystal Cave and The Last Enchantment. Even though this book is part of a series, it still stands on its own. All three books are masterfully written and very entertaining.