World War Z and the Zombie Survival guides are required.
Day by day was ok, too military good ol'boy for my tastes. Eden was the same way. I get that armed service members wrote the books, but I could really care less for the military code for the weapon the person is using.
Ex-heroes was a GREAT read. It's like Marvel zombies, but not in the Marvel universe. "Dead End" was good.
All the books but the first are by Permuted Press. They only do zombie/apocalypse books.