To avoid the necessity of typing them all out, I've copy-pasted all the books mentioned in the Wikipedia article on the Ballentine Adult Fantasy series, (I've put the ones I've read into bold, in case anyone is about to propose them as among the books unread by Chronicles members, and simply list the rest in plain text to see if anyone else has read them.)
The precursors to the series:
So I've read all the books they published before the series was officially a series.
- The Hobbit, J. R. R. Tolkien (August 1965)
- The Fellowship of the Ring, J. R. R. Tolkien (October 1965)
- The Two Towers, J. R. R. Tolkien (October 1965)
- The Return of the King, J. R. R. Tolkien (December 1965)
- The Tolkien Reader, J. R. R. Tolkien (September 1966)
- The Worm Ouroboros, E. R. Eddison (April 1967, later reprinted (5th) with colophon)
- Mistress of Mistresses, E. R. Eddison (August 1967)
- A Fish Dinner in Memison, E. R. Eddison (February 1968)
- The Road Goes Ever On, J. R. R. Tolkien and Donald Swann (October 1968)
- Titus Groan, Mervyn Peake (October 1968; later reprinted (5th) with colophon)
- Gormenghast, Mervyn Peake (October 1968; later reprinted (5th) with colophon)
- Titus Alone, Mervyn Peake (October 1968; later reprinted (4th & 5th) with colophon)
- A Voyage to Arcturus, David Lindsay (November 1968; later reprinted (2nd & 3rd) with colophon)
- The Last Unicorn, Peter S. Beagle (February 1969, with "A Ballantine Adult Fantasy" on the cover; later reprinted with colophon)
- A Fine and Private Place, Peter S. Beagle (February 1969, with "A Ballantine Adult Fantasy" on the cover of the first two printings)
- Smith of Wootton Major and Farmer Giles of Ham, J. R. R. Tolkien (March 1969)
- Tolkien: A Look Behind "The Lord of the Rings", Lin Carter (March 1969)
- The Mezentian Gate, E. R. Eddison (April 1969, with "A Ballantine Adult Fantasy" on the cover)
Volumes published as part of the series, based on a listing by Lin Carter in Imaginary Worlds: the Art of Fantasy .
(A number of these I started but just didn't care for them enough to finish, so don't count them as books I have read. Also, where the collections of writers like Clark Ashton Smith, Dunsany, and Lovecraft are concerned, I've probably read most of the stories in other collections but not these particular volumes, so again not counted. So that leaves about three quarters of the books in the actual series that I wonder if anyone here has read.)
- The Blue Star, Fletcher Pratt (May 1969) (#01602)
- The King of Elfland's Daughter, Lord Dunsany (June 1969) (#01628)
- The Wood Beyond the World, William Morris (July 1969) (#01652)
- The Silver Stallion, James Branch Cabell (August 1969) (#01678)
- Lilith, George MacDonald (September 1969) (#01711)
- Dragons, Elves, and Heroes, Lin Carter, ed. (October 1969) (#01731)
- The Young Magicians, Lin Carter, ed. (October 1969) (#01730)
- Figures of Earth, James Branch Cabell (November 1969) (#01763)
- The Sorcerer's Ship, Hannes Bok (December 1969) (#01795)
- Land of Unreason, Fletcher Pratt and L. Sprague de Camp (January 1970) (#01814)
- The High Place, James Branch Cabell (February 1970) (#01855-9)
- Lud-in-the-Mist, Hope Mirrlees (March 1970) (#01880-X)
- At the Edge of the World, Lord Dunsany (March 1970) (#01879-6)
- Phantastes, George MacDonald (April 1970) (#01902-4)
- The Dream-Quest of Unknown Kadath, H. P. Lovecraft (May 1970) (#01923-7)
- Zothique, Clark Ashton Smith (June 1970) (#01938-5)
- The Shaving of Shagpat, George Meredith (July 1970) (#01958-X)
- The Island of the Mighty, Evangeline Walton (July 1970) (#01959-8)
- Deryni Rising, Katherine Kurtz (August 1970) (#01981-4)
- The Well at the World's End, Vol. 1, William Morris (August 1970) (#01982-2)
- The Well at the World's End, Vol. 2, William Morris (September 1970) (#02015-4)
- Golden Cities, Far, Lin Carter, ed. (October 1970) (#02045-6)
- Beyond the Golden Stair, Hannes Bok (November 1970) (#02093-6)
- The Broken Sword, Poul Anderson (January 1971) (#02107-X)
- The Boats of the "Glen Carrig", William Hope Hodgson (February 1971) (#02145-2)
- The Doom that Came to Sarnath and Other Stories, H. P. Lovecraft (February 1971) (#02146)
- Something About Eve, James Branch Cabell (March 1971) (#02067-7)
- Red Moon and Black Mountain, Joy Chant (March 1971) (#02178-9)
- Hyperborea, Clark Ashton Smith (April 1971) (#02206-8)
- Don Rodriguez: Chronicles of Shadow Valley, Lord Dunsany (May 1971) (#02244-0)
- Vathek, William Beckford (June 1971) (#02279-3)
- The Man Who Was Thursday, G. K. Chesterton (July 1971) (#02305-6)
- The Children of Llyr, Evangeline Walton (August 1971) (#02332-3)
- The Cream of the Jest, James Branch Cabell (September 1971) (#02364-1)
- New Worlds for Old, Lin Carter, ed. (September 1971) (#02365-X)
- The Spawn of Cthulhu, Lin Carter, ed. (October 1971) (#02394-3)
- Double Phoenix, Edmund Cooper and Roger Lancelyn Green (November 1971) (#02420-6)
- The Water of the Wondrous Isles, William Morris (November 1971) (#02421-4)
- Khaled, F. Marion Crawford (December 1971) (#02446-X)
- The World's Desire, H. Rider Haggard and Andrew Lang (January 1972) (#02467-2)
- Xiccarph, Clark Ashton Smith (February 1972) (#02501-6)
- The Lost Continent, C. J. Cutcliffe Hyne (February 1972) (#02502-4)
- Discoveries in Fantasy, Lin Carter, ed. (March 1972) (#02546-6)
- Domnei: A Comedy of Woman-Worship, James Branch Cabell (March 1972) (#02545-8)
- Kai Lung's Golden Hours, Ernest Bramah (April 1972) (#02574-1)
- Deryni Checkmate, Katherine Kurtz (May 1972) (#02598-9)
- Beyond the Fields We Know, Lord Dunsany (May 1972) (#02599-7)
- The Three Impostors, Arthur Machen (June 1972) (#02643-8)
- The Night Land, Vol. 1, William Hope Hodgson (July 1972) (#02669-1)
- The Night Land, Vol. 2, William Hope Hodgson (July 1972) (#02670-5)
- The Song of Rhiannon, Evangeline Walton (August 1972) (#02773-6)
- Great Short Novels of Adult Fantasy I, Lin Carter, ed. (September 1972) (#02789-2)
- Evenor, George MacDonald (November 1972) (#02874)
- Orlando Furioso: The Ring of Angelica, Volume 1, Ludovico Ariosto, translated by Richard Hodgens (January 1973) (#03057-5)
- The Charwoman's Shadow, Lord Dunsany (February 1973) (#03085-0)
- Great Short Novels of Adult Fantasy Volume II, Lin Carter, ed. (March 1973) (#03162-8)
- The Sundering Flood, William Morris (May 1973) (#03261-6)
- Imaginary Worlds: the Art of Fantasy, Lin Carter (June 1973) (#03309-4)
- Poseidonis, Clark Ashton Smith (July 1973) (#03353-1)
- Excalibur, Sanders Anne Laubenthal (August 1973) (#23416-2)
- High Deryni, Katherine Kurtz (September 1973) (#23485-5)
- Hrolf Kraki's Saga, Poul Anderson (October 1973) (#23562-2)
- The People of the Mist, H. Rider Haggard (December 1973) (#23660-2)
- Kai Lung Unrolls His Mat, Ernest Bramah (February 1974) (#023787-0)
- Over the Hills and Far Away, Lord Dunsany (April 1974) (#023886-9)
Two volumes published after retirement of the Unicorn's Head colophon were evidently intended for the series. The first has a Carter introduction and the second completes a set of four begun under his editorship.
- Merlin's Ring, H. Warner Munn (June 1974)
- Prince of Annwn, Evangeline Walton (November 1974)
Ive read 27 of the books on that list.