There are several great books told from the perspective of Queen Guinevere and other women in the King Arthur legend.
Queen of the Summer Country Series, by Rosalind Miles: (Guinevere)
Queen of the Summer Country
Knight of the Sacred Lake
Child of the Holy Grail
Queen of the Western Isle Series, by Rosalind Miles: (Isolde)
Queen of the Western Isle
Maid of the White Hands
Lady of the Sea
Child of the Morning Spring Series, by Persia Wolley: (Guinevere)
Child of the Morning Spring
Queen of the Summer Stars
Guinevere: The Legend in Autumn
The Mists of Avalon, by Marion Zimmer Bradely (Morgaine and Guinevere)
There is also:
In Winter's Shadow by Gillian Bradshaw (an excellent portrayal of Guinevere)
The Guinevere Trilogy by Sharan Newman
Guinevere
The Chessboard Queen
Guinevere Evermore
Guinevere by Laurel Phelan
The Tales of Guinevere by Alice Borchardt
The Dragon Queen
The Raven Warrior
(not sure if the series was ever finished)
Gwenhwyfar by Mercedes Lackey
The House of Pendragon series by Debra A. Kemp (told from Arthur and Gwenhwyfar's daughter's point of view)
The Firebrand
The Recruit
She was a queen.
no
Camelot
Lancelot
Guinevere
Lancelot was a legendary knight of the round table and lover of Queen Guinevere.
Queen Guinevere.
A.D. 960
A.d 960
yes
5
King Arthur