Fortress — Jack Hunt

After tackling vicious city gangs, hordes of the undead and escaping Salt Lake City, this daring band of misfits are forever changed. But the nightmare of this apocalypse is not over. Torn apart as a group, but having gained new allies, they must now battle for survival as they head to NORAD. But when they stumble on a group who offer safety within a fortress, and another that seeks to kill, one hasty decision may destroy them all.