“Four adventurers find themselves at Carcasilla, earth’s last citadel, a billion years from now. It is there that the mutated remains of humanity are making their final stand.” — GoodReads.com
“It’s all about a quartet of people — two Allies, and two agents for the Axis — who stumble upon a mysterious craft in the North African desert, and are catapulted into the far far future, where they end up in conflict on a dying Earth against the mysterious alien “gods” who control a specially-bred species of pet humans from their towering citadel.”
Alex Schomburg – Earth’s Last Citadel, 1964