The 3 titles in the terrific (imo) Last Policeman Trilogy
by Ben H. Winters are currently on sale at Amazon for $1.99 each.
The Last Policeman
Winner of the 2013 Edgar Award Winner for Best Paperback Original
https://www.amazon.com/gp/product/B0076Q1GW2/
Countdown City
Winner of the 2014 Philip K. Dick Award
https://www.amazon.com/gp/product/B00B6OV90E/
World of Trouble
Nominated for the 2015 Edgar Award for Best Paperback Original
https://www.amazon.com/gp/product/B00HXYHVNU/