Lest Darkness Fall (Sphere science fiction)

Archeologist Martin Padway is visiting Rome in Italy. He is struck by lightning and catapulted back to Rome of the sixth century A.D. The Western Roman Empire has fallen to the Goths, and civilization teetering on the brink of falling into the Dark Ages. As Mysterious Martinus, can Martin win through the life and death perils of religious controversy, political intrigue and international diplomacy to twist the course of history and avoid that fall into darkness? This is a science fiction classic.