This image was modified from the cover of The Moon Pool.

       The Moon Pool by A. Merritt. Published Avon Books in 1951. Originally published in hardcover by Liveright in 1919. Cover artists unknown. According to the New York Times, the book wove together ancient legends with the scientific knowledge of the times. "Into a lost land of incredible marvels, spine-tingling witchcraft, and horrifying monster-men, came four adventurers. But between them and their conflicting goals stood a mystery as old as the stars - and as terrible as the inferno - the maddening, radiant, evil enigma of "The Shining One."

        This description from Kaplan, B. J. ed. (1990) "Love was Cheap and Life was High: Postcards from paperback cover art of the 40s and 50s" Collier Books.