Mary Stewart's Merlin Trilogy+

The Crystal Cave (Arthurian Saga, Bk. 1), Mary Stewart, Ballantine Books, August 1996, ISBN: 0449911616 Paperback
The Hollow Hills (Arthurian Saga, Bk. 2), Mary Stewart, Ballantine Books, August 1996, ISBN: 044991173X Paperback, 498 pages
The Last Enchantment (Arthurian Saga, Bk. 3), Mary Stewart, Ballantine Books, August 1996, ISBN: 0449911764 Paperback, 538 pages
Or select all three books in
Merlin Trilogy , Mary Stewart, William Morrow & Company, December 1980, ISBN: 0688003478 Hardcover, 919 pages
The Wicked Day (Arthurian Saga, Bk. 4), Mary Stewart, Ballantine Books, August 1996, ISBN: 0449911853 Paperback, 452 pages