The house looked strange […] Like it was the empty, two-story tomb of some runaway zombie. (Prologue.1.1)
No, it's not an episode of The Walking Dead. It's Paul's house—or at least, Paul's house as it seems to him. Did they forget to take down the Halloween decorations or something?
Maybe, but zombies show up again as they drive off. Paul feels as if an angry zombie is following him to Florida: "I started thinking about a zombie, a pissed-off zombie. Dragging one foot behind him. […] Slowly, surely, stalking his way down Interstate 10" (1.1.56). So what's up with these zombies?
Well, a zombie is something that should be dead, but isn't. And it's totally terrifying, because it won't die, no matter what high-power military weapons you try shooting it with, or what brand of shovel you hit it over the head with. Just like Paul's past! (Except for the shooting and head-bonking parts.)
If he can't even remember what happened to his eyes, he can't even put it to rest. (You know, bash it in the head.) And it seems even scarier when he can't see it quite clearly—like a zombie off in the distance. And it follows him wherever he goes, just like a zombie. So, for Paul, zombies = his creepy past.