What a huge disappointment. It was a solid 4 stars for the first half of the book and then it went completely downhill. I don't want to give away the story so I'll just mention some impressions.
John and Mason had zero connection whatsoever. They started off with great chemistry and the sexual tension was palpable. After the classic initial fall out, I was waiting for some angsty, dramatic reunion where the characters would slowly come closer emotionally. It never came. John's apathy and aloofness reminded me of Boyd in the first chapters of ICoS. But John's character never grew or matured, like Boyd eventually did. He just stayed dry and flat until the very end. As for the actual plot development, it became very hocus pocus for me, which was a major let down, because I really think it could have turned out more atmospheric and otherwordly than it did. The erotic scenes were weird, which was extremely surprising to me because I've read quite a few of Mitchell's books and the erotica is usually very steamy and hot. Here, the scenes felt very clinical and as if the characters were disconnected. I was feeling pretty disconnected myself by the end. Good idea but very badly executed.