Zarkon, Lord of the Unknown in Invisible Death A Case from the Files of Omega
Doubleday, 1975, first edition hardcover with dustjacket. This is the second in the "Zarkon" series of pulp adventure novels modeled after "Doc Savage." Other novels in the series are: "The Nemesis of Evil" (1975); "The Volcano Ogre" (1976); "The Earth-Shaker" (1982) and "Horror Wears Blue" (1987).