The Chrysalids

"Long, long ago lived the Old People. No one knew just how long ago - perhaps two thousand years. We knew that they had many things we no longer had, like mines and high-powered engines and machines. But something terrible had happened to the Old People. It was worse than fire and earthquakes. We called it the Tribulation. Nearly all the Old People had died in the Tribulation. Our world was divided into two parts. We lived in a land called Labrador. We had farms and fished in the sea. The sea lay round the north and east of Labrador. South of Labrador were the Badlands where the Tribulation had brought the Old People to their end. There was nothing but ruins. And if you went to the Badlands you died. But in many ways Labrador was not safe either..." -back cover.