I liked the book, but I like the Night Huntress series a lot more. I thought that the romance between Denise and Spade seemed a little abrupt. There was less building up to it. Jeaniene Frost probably knew (or had planned) that the Night Huntress World books would each be stand alone books that only enhance the original series. This book did successfully fill my time while I am waiting for Night Huntress #5. 
 I've seen some reviews that don't like the way that Cat is in this book, and I can agree with that. She doesn't seem like herself. With that note, however, this story is not told from Cat's (or Bones') point of view (1st or 3rd person). I knew that they were going to make and appearance in the story and I was looking forward to seeing them from someone else's perspective. What did Spade or Denise think about Bones and Cat's relationship? While we did get that a little I think that circumstances were a little to tense (story wise) for Spade or Denise to sit there and contemplate Cat and Bones. I can forgive that because it's not a Cat and Bones story, it's just told in their world and they make an appearance. 
 Something else I would've liked to have seen would be a scene between just Cat and Denise. The whole scene where Bones talks to Denise about her ideas of changing (or not)into a vampire would have been nice coming from Cat who (as we know from Destined for an Early Grave) just became a full fledged vampire (even though she is still uniquie with that too). Cat could give her reasons to Denise for why she did what she did although I did like what Bones had to say on the matter. Anyway, it would have been nice to have a true friendship moment between Cat and Denise since we are told (more than once in both series) that Denise is "Cat best friend". 
 The storyline / plot itself was nicely done. I like fresh idea (in the Night Huntress series) of Demons. We hadn't really touched on that topic in the series at all. Night Huntress has been mainly about Vampires / Ghouls with other creatures (ghosts) floating in and out at random. It was nice to see that change. 
 As far as the characters go, I liked Spade from the Night Huntress series, I thought in that series he seemed really mysterious. I didn't really expect him to turn out to be the character he ended up being in this story (if that even makes sense), but I still liked him. Denise on the other hand we didn't really see that much of in the Night Huntress books, but I liked her enough. I liked that she was a strong-willed heroine not willing to be all pouty and sad, at times though I thought that she was too rash with her decisions. She liked to make decisions before she knew the whole story as it were. 
 Another thing that I liked about the book was getting to see where Cat and Bones were in their lives. I liked that it took place after the events in Detined for an Early Grave. It was nice to see that they were both ok because that book (if you've read it) really sent me for an emotional rollercoaster when it came to those two. 
 I know that she's written Mencheres story but I don't know if I will buy that one. What worked here is that I like / wanted to get to know more about Spade and Denise. I don't know if I want / need to get to know more about Mencheres. The only way I would probably read that one is if Bones and Cat made and appearance in it as well. But I like that I have that option. Theses stories will not effect the plotline going in the main series.