Source Code: Echoes of the Apocalypse

First it developed a fever, then it began to cough, and finally it fell silent amid endless chaos and flames. War, plague, climate upheaval... Disaster after disaster fell like a row of dominoes, bringing down the fragile edifice of human civilization. When the survivors crawled out of the ruins and shelters, they found a world utterly remade: radioactive deserts, mutated jungles, the rotting skeletons of cities, and plants and animals that were both familiar and strange, struggling to survive in the new environment.

They called this age the "Scorched Earth Era," following the "Great Collapse."

No System + high IQ + wasteland fiction + no self-righteous saint