Finally! A Mercy Thompson book that didn't include storylines with animal sacrifice. The last few books before this had me seriously hesitant to continue with the series, and even after buying this, it stared at me for about a week before I picked it up with the intention of putting it right back down again if it even looked at an animal the wrong way.
Fortunately – and unfortunately – I never had to put the book down. At least, not until 2.30am when I finally gave into sleep, only to pick it up again the next morning and finish it off.
That's not to say the story was perfect; it was good, but the sub-plot between Mercy and Adam was meh, and got terribly schmaltzy towards the end (keeping in mind I have a low tolerance for "the power of love").
The main plot concerned something that got out of Underhill and started possessing people, making them kill others, before it killed them and moved on. This was more interesting to me, although it never really achieved 'gripping'. And towards the end, but long before the climax, I guessed who the smoke demon was, which was both a tiny bit disappointing, and also - YAY! I was right! - making it a wash overall.
Generally, I enjoyed the story and it restored my faith in the series. I hope book 13 stays away from the witches, although with that number, I don't like my chances.