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20th century
King Arthur and his Knights by Maude Radford
Arthur Rex: A Legendary Novel by Thomas Berger
Taliessin through Logres (1938) and The Region of the Summer Stars
The Mists of Avalon by Marion Zimmer Bradley
The Road to Avalon by Joan Wolf
The Child Queen, The High Queen, (collected in Queen of Camelot), Prince of Dreams, and The Grail Prince by Nancy McKenzie
Hallowed Isle by Diana L. Paxson
Sword at Sunset by Rosemary Sutcliff
Also The Sword and the Circle'
Mordred's Curse and Merlin's Gift by Ian McDowell
I am Mordred and I am Morgan le Fay by Nancy Springer
The Guenevere novels by Rosalind Miles
Guenevere, Queen of the Summer Country
The Knight of the Sacred Lake
Child of the Holy Grail
Knight Life, One Knight Only and Fall of Knight by Peter David
The Merlin series by Mary Stewart
The Crystal Cave
The Hollow Hills
The Last Enchantment
The Wicked Day
The Prince and the Pilgrim
The Arthor series by A. A. Attanasio
The Dragon and the Unicorn
The Eagle and the Sword
The Wolf and the Crown
The Serpent and the Grail
The Warlord Chronicles by Bernard Cornwell
The Winter King
By Jane Yolen:
Sword of the Rightful King
The Young Merlin Trilogy
By Gerald Morris:
The Squire's Tale
The Squire, His Knight, and His Lady
The Savage Damsel and the Dwarf
Parsifal's Page
The Ballad of Sir Dinadan
The Princess, the Crone, and the Dung-Cart Knight
The Lioness and her Knight
The Quest for the Great Unknown
By Molly Cochran and Warren Murphy
The Forever King
The Broken Sword
The Third Magic
The Pendragon Cycle by Stephen Lawhead
Taliesen
Merlin
Arthur
Pendragon
Grail
Avalon
21st century
Avalon High by Meg Cabot
)
The House of Pendragon I: The Firebrand by Debra A. Kemp (2003)
The House of Pendragon II: The Recruit by Debra A. Kemp (2007)
Sword of Darkness by Kinley MacGregor
MacGregor
Sons of Avalon: Merlin's Prophecy by Dee Marie
The Rose of Camelot by James Philip Cox
Camelot Lost by Jessica Bonito
I am Morgan le Fay: A Tale from Camelot by Nancy Springer
Nonfiction
Arthur's Britain by Leslie Alcock
The Return From Avalon by Raymond H. Thompson
The Quest for Arthur's Britain by Geoffrey Ashe
The Medieval Quest for Arthur by Robert Rouse and Cory Rushton
King Arthur - The True Story by Graham Phillips and Martin Keatman
Pendragon The Origins of Arthur by Steve Blake and Scott Lloyd
The Arthurian Tradition by John Matthews