Zombie Killers: Civil War (Zombie Killer Blues Book 4)

Four years after the Undead virus / parasite infected the world, civilization struggles on. The United States lives, with forty million people crammed into the Pacific Northwest, living in squalid refugee camps. Army units have made inroads into the ruins of the rest of America, working on clearing the major cities.
Outside America, England survived, as did other island nations. The survivors are struggling back to their feet, fighting a long, exhaustive campaign to regain the Japanese Islands and Europe.

On an island in the Hudson River, thirty miles north of the nearest Army outpost, several families have homesteaded. Mixed military and civilian, planting crops and salvaging the land they are survivors of the Army€s elite scout teams. Children are born, old friends mourned, rivers run clean and corn grows in the ruins.

The fight, though, still goes on...