You Cannot Change the Laws of Physics
Well, maybe the laws of physics can be changed. At least they can be in author S. M. Stirling's Emberverse series. It all starts in Dies the Fire. An electrical storm centered over the island of Nantucket has rendered all electrically powered devices useless and firearms inoperable. The works changes in an instant as people band together in feudal groups to survice. The story continues in The Protector's War, A Meeting at Corvallis, The Sunrise Lands, and The Scourge of God.
What is your favorite post-apocalyptic book?