4.5 stars. I could hardly put it down, but I subtract a little because books I find amazing can be bleak, but I prefer more spots of joy and hope in there too. It's a great book, but not a happy one. And I really don't like those people on the cover. 
 I loved how Revis incorporated a mystery again. She continued this story in a well-thought-out way, even though I found myself re-reading lines at times to make sure I was getting it. Amy and Elder are both very real in their confusion and inconsistencies. I love this series for its outer space setting, and I'm really looking forward to the next one.