Eat Slay Love by Jesse Peterson

"Sarah and David have survived the zombie apocalypse. They stood side by side and fought the undead, mad scientists, and even bionic monsters until the unthinkable happened. A zombie bite. But not even that could stop them. Now, with a possible cure in hand, they're headed east, looking for a safe zone behind the rumored "Wall." They're feeling pretty optimistic.

That is until Dave stops sleeping and starts lifting huge objects."

Mass market, a nice copy!