So, I'd give this book five stars, but there are two things holding it back: The concept is something I could NEVER see happening and while I liked the characters, I didn't love any of them. They were likable for me, but not lovable, if that makes sense. 
 That said, there actually was a decent explanation at one point for how unwinding came about and I kind of liked that whole angle to it. 
 The book itself is very engaging and I finished it pretty darn quick considering what little time I have for reading nowadays. It also did some things that I felt really pushed boundaries and it really went beyond typical YA. It was dark and truly scary. I like how at one point I was truly terrified, but it ended up being the total opposite. The ending really sold it, I teared up, it was such a unique and interesting concept. 
 Really, this is very very close to five stars. The only reason I don't rate it that way is that while I enjoyed it a lot, it didn't reach that point that made it tip over the edge into love and make it a favorite. But it's still fantastic and a book I'd recommend to others.