[Shadekeep]

Naturally there are the expected influences of Tolkien et al, but apart from those the fantasy novels that most reminded me of Cidri are Roger Zelazny's Amber books. There are certain parallels between the Amberites and the Mnoren, though by no means identicality.

I like to draw inspiration from pastoral fantasy novels, such as the Zimiamvia books by E. R. Eddison and the fantasy writings of Jack Vance. I also draw on classic fantasy/supernatural fiction by H. P. Lovecraft, William Hope Hodgson, and various Gothic period authors.

One series of books that was an interesting influence on a campaign were the Well of Souls books by Jack L Chalker. While these are science fiction, they are a lot of fantasy elements and races in them. And the world is laid out as a series of huge hexes. ^_^

One other series that mixes fantasy and science fiction, and which makes a different kind of campaign setting, are the Gaea novels by John Varley.

It's also fun teasing out where elements of the original In The Labyrinth seemed influence by books. I believe the Goo is inspired by a similar creature in the Magic Goes Away series by Larry Niven (though giant amoebae exist elsewhere in fiction too, including Star Trek), and the Slinker seems inspired by the creature of the same name from Mad Moon by Stanley G. Weinbaum.