In reading order
Giant
T. A. Barron
Merlin: The Lost Years, Book 1
T. A. Barron
Merlin: The Seven Songs, Book 2
T. A. Barron
Merlin: The Raging Fires, Book 3
T. A. Barron
Merlin: The Mirror of Fate, Book 4
T. A. Barron
Merlin: The Wizard's Wings, Book 5
T. A. Barron
Merlin: The Dragon of Avalon, Book 6
T. A. Barron
Merlin: Doomraga's Revenge, Book 7
T. A. Barron
Merlin: Ultimate Magic, Book 8
T. A. Barron