Jeff Shanks digs into a vast sink hole of Atlantean literature that was current in Howard’s time. For more information on the theosophy movement in literature you might want to check out this title Sinking The Atlantis Myth. All of these old ethnographic theories have been superseded, or sunk Atlantean like, by modern archeology and the mapping of the human genome. But they are fun.
Also two fiction works set around the Atlantean concept are The Magic Goes Away by Larry Niven—a truly excellent novel, and Thongor Against the Gods by Lin Carter