From publisher blurb:
Ruins of Atlanta adds setting information to the Kalos universe, focusing in detail on the people who have chosen to live in the aftermath of the Fall of Paragon, when that hero single-handedly destroyed the city of Atlanta.
The ruins of Atlanta offer an unusual opportunity to combine superhero roleplay with the post-apocalypse genre. Many of the tropes of the post-apocalypse genre are present here: lawless gangs of scavengers, young idealists trying to build a better world, jaded cynics who will do anything to survive, power-hungry warlords, religious fanatics, high-tech enclaves, and even the occasional mutant.
Welcome to the ruins.