I do not like ghost stories. I will not read horror or go to scary (or even scarey) movies. I used to close my eyes when Captain Hook threatened Peter Pan, and am not a fan of Weeping Angels. Lovecraft is not my friend. When I first heard that this book was out and so well received, I put it on my wishlist, until I found out it was a ghost story. I then took it off. But the reviews and recommendations haunted me, so I finally picked up a copy at our local UBS. What I found was an amazingly good book: well written, thought provoking, interesting plot, and best of all, a male protagonist in a YA book. That's a rare combination. It will keep me reading more by Kendare Blake, whether it has Cas in it or not.
Other reviews will give you plot summaries. What you'll get from me are just three words: read this book.