I don't think I saw a spoiler version, but feel free to link me to it.
Overall, I think it just fell flat. There were some suspenseful times, but they all revolved around the presence of the creatures which we know NOTHING about. I was swearing telling DH about the book. We don't know where they came from, what they are, how big or small. Olympia mentions them being beautiful, but that's all that's given.
The story was somewhat interesting, but her obsession with Tom was a little unnerving. I saw through Gary immediately. Was it that he was already 'crazy' that he didn't follow suit with everyone else? I pictured Sam Healy from OITNB as Gary for some reason.
When I reached the end, at first I was relieved that she found safety but a few minutes after I finished and started doing other things I just went WTF? We don't know anything about them!
There were a few suspenseful scenes (the bar and her blindfold), but mostly I just kept wanting to know why everyone else died besides the obvious answer.