Sanctuary by Greg Rode (Book 4 of Sanctuary Chronicles)
"We have no clue what we're about to discover, but it will lead us to everything else."
The good news: we finally killed all the local zombies. The not-as-good news: I've been bitten. But assuming all goes well, and no one has to shoot me in the face, we'll finally have peace, quiet, and sanctuary ... until we decide to go play golf, where we make a stomach-turning discovery and run headlong into a deeply traumatic experience from Morgan's past. And Morgan being Morgan, this means she's going to pick a fight, which turns into another (reluctant) group road trip.
We're going to go back to the fortress she stopped at on her cross-country trip and save the people trapped there from Marcus, his thugs, and their twisted ideas, even though we're outnumbered like usual. We've got a solid plan to rescue the people who want to leave and bring them back with us. Then everything will be totally great. Of course, nothing is simple or goes according to plan.
It's a battle on two fronts this time—one against humans, the other against zombies--and it's going to take everything we have to survive.
It's kill or be killed.