The Anguished Dawn

After a near miss by a white-hot protoplanet, Earth is devastated, civilization as we know it has ended, and the survivors are reverting to barbarism. Only the Kronian colony on Saturn's moons preserves technology and human culture. Landen Keene, taken off the Earth before the disaster, is a key figure in the Kronian efforts to rebuild civilization on Earth. Then he finds that other survivors from Earth miss the power they once wielded, and are bent on restoring the old privileges and hierarchy, with themselves at the top. And if subtle methods fail, they won't hesitate to use the violent tactics that served them well back on Earth...