The story, ah the story. You start piecing things together, reading different snippets or listening to audio recordings scattered across the map. However, you never actually get a satisfying explanation for this apocalyptic event, and you won't understand why barbed wire turns demented people into shambling monstruosities.
The plot states that somehow, through unexplained means, the primary antagonist has the ability to literally warp reality, and that kills pacing and setting. Yeah, it allows you to go from village to hospital basement in a second, but it doesn't really let you get immersed in the world around you.
As for the characters. They're there. You talk to them, they reply. Not much else.
Castellano's shtick is his detectivey look, and that's pretty all the character development you'll get. You get some info on him, but it's something like "He wanted to be a detective instead of a cop, because he can help people and get a better pay." Brilliant motivation right?
The rest of the cast isn't faring any better. Except the visual characterization, of which there's plenty, these characters have nothing going for them. Paint drying is more entertaining than they are. Probably more developed too.