This article is from the Arthurian Booklist FAQ, by Cindy Tittle Moore firstname.lastname@example.org with numerous contributions by others.
Haar (Hoar?), J. T. King Arthur (New York: Crane Russak, c.1967,
Haldeman, Linda. The Lastborn of Elvinwood. Garden City, NY:
Hanratty, Peter, The Book of Mordred and The Last Knight of Albion
(Ace Fantasy and Bluejay Books. ISBNs 0-441-07018-3 and 0-312-94271-8.
Paperback and trade paperback.) A retelling of the Arthurian legend in
a bizarre mix of modern and ancient times.
Hanson, Charles Henry, Stories of the Days of King Arthur (With
illustrations by Gustave Dore, T. Nelson, London/Edinbugh/New York,
Hastings, Selina, Sir Gawain and the Loathly Lady (Lothrop, Lee &
Shepard Books, New York, 1985). ISBN 0-7445-0295-0. This is
beautifully illustrated. The inside cover says that a version of Sir
Gawain and the Green Knight is also available by the same author.
Hawke, Simon [Nicholas Yermakov], The Wizard of 4th Street (1987), The
Wizard of Whitechapel (1988), The Wizard of Sunset Strip (1989), The
Wizard of Rue Morge (1990), The Samurai Wizard (1991), The Wizard of
Santa Fe (1991), The Wizard of Camelot (1993). New York, Warner Books.
Premise: There was a magical alien species which bred with humans
long, long ago. The descendants of these unions were humans with
magical abilities. Merlin was a half-breed, as was Morgan LeFay. Since
magic and technology cannot co-exist, magic went dormant as technology
increased. After the fall of technology, magic returned and Merlin
revived. Unfortunately, the alien species discovered that Necromancy
produces powerful magic and they are now known as demons. Merlin has
to recruit and train magical humans to thwart their plans. Appearances
by Merlin, Morgan Le Fay and Mordred.
Heller, Julek and Dierdre Headon. King Arthur & His Knights. Fiction
which draws on a variety of sources including, but not limited to
Chretien de Troyes' Arthurian Romances & Malory's Morte D'Arthur.
Dragons' World Ltd. 1990 ISBN 1850281149.
Hollick, Helen. Kingmaking, Pendragon's Banner, a third book due in
June 1997 to complete the trilogy.
Humble, William F. A Tale of Arthur (Anthony Blond, London, 1967).
Hunter, Jim. Percival and the Presence of God. London and Boston:
Faber and Faber, 1978.
Jeter, K. W. Morlock Night. New York: DAW Books, 1979.
Johnson, Barbara Ferry. Lionors. New York: 1975.
Jones, Courtway, In the Shadow of the Oak King. It apparently tries to
tell the story in a historically 'realistic' setting (i.e., without
grafting the high middle ages onto sixth century Britain).
Jones, Courtway. The Witch of the North. New York: Simon and Schuster,
1994. Copyright: 1992. Sequel to In the Shadow of the Oak King.
Jones, Mary J., Avalon (The Naiad Press, ISBN: 0-941483-96-7, 1991).
This is set in the closing days of King Arthur's reign and mostly
concerns the Lady of the Lake at that time (Argante, from Layamon; her
predecessor is Nimue), with some recounting of her childhood.
Definitely a feminist reading, and not as well done as Mist of Avalon,
for example. It is also curiously incomplete. More books may be
Kane, Gil and John Jakes. Excalibur!. No relation to film of same name
and approximate year.
Karr, Phyllis Ann. The Idylls of the Queen. New York: Ace Books, 1982.
Katz, Welwyn Wilton, The Third Magic (Groundwood Books/Douglas &
McIntyre, ISBN (bound): 0-88899-068-5 (pbk): 0-88899-126-6, 1988). A
"young adult" book, this one has one of the more imaginative
retellings of the Arthurian legend.
Kennealy, Patricia, The Hawk's Gray Feather, The Oak Above the Kings,
and The Hedge of Mist. (ROC (division of Penguin Books), ISBN
0-451-45053-1, 1990). Builds upon the world of The Silver Branch, The
Copper Crown and The Throne of Scone in which the Sidhe were aliens.
This book is set much earlier. A good fantasy/SF blend.
Kuncewicz, Maria. Tristan: A Novel. New York: George Braziller, 1974.