The Valley-Westside War (Crosstime Traffic)

the long version

In The Valley-Westside War, a global nuclear war broke out in 1967, leading to the collapse of civilization. The book is set in the ruins in what was once Los Angeles, 130 years after the war. The area of the city is controlled by two rival feudal states at war with one another: the Kingdom of Westside and the Kingdom of the Valley. The Crosstime Traffic team is dispatched to investigate the remains of the UCLA library in an attempt to discover what happened to cause the initial nuclear war, but are caught up in the local war by citizens of both kingdoms who believe that they are trying to access the knowledge of the old people to create advanced weapons.