The Zombie Chronicles - Book 5 - Undead Nightmare. The Zombie Chronicles, #5

This is the longest book so far in The Zombie Chronicles at nearly 80, 000 words. Blurb:My name is Dean Walters and I'm eighteen years old. We had saved Val, Jackie, and Claire with the precious vials in our possession, but they weren't 100 percent effective. Those who had taken the serum, the so-called miracle cure for zombie-itis, were easy enough to spot, since they had glowing green eyes and were suddenly equipped with night vision that would have made the average bat jealous, but that was only one side effect.
Much to our dismay, the other side effect wasn't quite so tolerable. Some cured people turned back into zombies but retained control of their reasoning, logical minds, virtually turning them into cannibals capable of thinking, calculating, stalking, and killing their victims. We'd decided to call them hybrids, and I feared that my sister, my girlfriend, and my potential future cousin-in-law were about to morph into just that.
Is it only a matter of time? Does that happen to everyone who takes the serum, or are some immune to that side effect? Our only hope for answers was to go to the lab, and I hoped the answers we'd finally get would be honest-and good news.