*3.5* This is a quick sci-fi mystery that is definitely fast-paced and brings up some interesting points about the fear of losing one's memories and self. I will say, I figured out who the unknown antagonist was about halfway through the book. The premise is definitely striking, but I found the execution a bit lacking. I think I would have liked this book to be a little bit longer and to explore more. It went by pretty quickly, and I think the reveal would have been a bit less shocking if more character development and possibly world-building had occurred. Otherwise, it's definitely not a bad read.