My favorite so far!
Mary and Jack have a dislike of each other (but do they really?) ever since they've met. This takes place about 2 years after the events of Winterblaze. Jack is a Regulator and Mary has newly moved into the same position after "graduating" from being Poppy's assistant. They partner up to find a murderer.
I really like the mix of paranormal historical romance with a side of steampunk thrown in. It really works for me and I love it. It's not quite a 4.5-5* read for me mainly because the main conflict between Mary and Jack could have been at least partially solved with a nice, long, honest conversation. Instead assumptions were made and well, there you go. Yes, there were "reasons" behind it; but isn't that always the case?
I also like that each book is about a different couple and the end of this links to the next book and couple.