Rot and Ruin - Jonathan Maberry

Nearly fourteen years ago a freak virus swept across the world turning those infected from the living into the undead. Benny Imura has grown-up never knowing anything different; his last memories of his parents tainted by the image of them becoming zombies. Now Benny is fifteen, and his brother Tom wants him to join the "family business" and train as a zombie killer. The last thing Benny wants is to work with Tom —- but at least the job should be an easy ride. Then the brothers head into the Rot and Ruin, an area full of wandering zombies, and Benny realises that being a bounty hunter isn't just about whacking zombies. As he's confronted with the truths about the world around him, Benny finds his beliefs challenged and makes the most terrifying discovery of all, that sometimes the worst monsters you can imagine, are human...