Hocus-Pocus Universe — Jack Williamson

Into the world of facts and figures, scientists and soldiers, came Eon Hunter. Eon the misfit, with his stubborn refusal to accept the world as it was; Eon the enigmatic, who always returned to involve himself in Guilborn's life. They loved the same girl, but were opposites in every other aspect. And Guilborn the scientist now has a theory that may prove to be the salvation of Earth. But Eon is convinced it will destroy it!