Check out this review and more at On the Wings of Books 
 What I Thought... 
 * Similar to the first book, The Naturals, Killer Instinct runs through like a episode of Criminal Minds. I really enjoyed the mystery and all it's twists and turns. This particular case reminded me a bit of an old NCIS episode, which is one of my favorites, so I loved the twists. 
 * Even though Cassie is the narrator, Killer Instinct focuses a lot on Dean. The case intertwines with Dean's father, who is a serial killer. We learn so much more about Dean in this book, and I wish he had been the narrator, I would have loved to have been up in his head instead. 
 * The fact that Killer Instinct focuses on Dean I wonder if the other books in the series will focus on the other Naturals as well. 
 * I love the Naturals group as a whole. They are all so different, but not at the same time and I think that even though they don't always get along they are a great group and work well together to find the killer. High school kids catching serial killers is fairly unbelievable, but if you can suspend belief than you will enjoy the mystery in Killer Instinct. 
 * I don't particularly care for the love triangle, even though it's more of a legit triangle than say, Twilight. Cassie does make a choice at the end of the book, and I'm ok with it, but I wish she hadn't made a choice. I feel like the group would work better if there were no romantic entanglements, but that's just how I feel. 
 Overall Killer Instinct is a quite the thriller and fans of Criminal Minds will enjoy this!