Because I've been doing too much re-reading lately, I'm starting a unit in which I'm not re-reading... well, only re-reading one book.
Some of these books I have heard of, some I haven't. Some I am pulling from the account in The Magician's Book of what Lewis and Tolkien read as kids.
I think I've put together a pretty decent list:
Phantastes by George MacDonald, 1858
The Well at World's End and/or The Wood Beyond the Worlds by William Morris 1894/1896
The Worm Ouroboros by Eric Rücker Eddison, 1922
The King of Elfland's Daughter by Lord Dunsany, 1924
Lud-in-the-Mist by Hope Mirrlees, 1926
The Coming of Conan the Cimmerian by Robert E Howard, (Short story compilation, originally published 1932-36)
(FYI: Hobbit published: 1937)