I listened to this as a recorded book. The reader (I can't remember who it was) did a superb job. The technical writing of the book (as read) was very good, excellent even, Patrick Ness is certainly talented, just look at his book A Monster Calls, but I didn't like the story that the writing told in this book. 
 Some problems I ran into: 
 I didn't like the main character. 
 One of the characters kept going so long after being attacked by so many things that I thought maybe this was going to turn into a zombie book, or a sci-fi-they've-learned-the-secret-living-forever books, but, no, that wasn't the case. 
 There were two extremely cruel deaths, and I don't know what purpose they really served. 
 My suspension of disbelief was tried too many times. 
 (SPOILER ALERT!) And I'm not sure I was buying whatever the story was trying to sell in terms of (SPOILER ALERT!) the main character's ability to kill. I'm not one for violence, but I was rooting for a specific character to be killed by ANYONE - especially by the main character - but for some reason he had to remain pure and not give in to murder because that's what the bad guys wanted him to become, a murderer. If you're defending yourself and the ones you love, though, it's not murder, especially under the circumstances the main character faced. And by playing whatever game the bad guys had set forth, and by their rules, he'd lost anyway. Why should he care what they would feel if he killed this madman who kept chasing him and attacking him? Kill the guy and get on with your effing life! (END SPOILER ALERT) 
 So I've given this book three stars, which is what I come up with when averaging a two for the story with a four for the writing.