I think that my main problem with this book is that its predecessor was such a fraught book - featuring death, duelling, betrayal and the love between Cat and Bones overcoming their trials - that this one fell a little flat.
The blurb itself is a touch misleading as there is more than one foe, and for the main enemy, formidable that she is, she featured very little in this book, which basically picks up not long after the last, just after Cat and Bones have been having some quality time together following their ordeal, and immediately after Mencheres and Kira have fallen in love. In fact, this couple appears so much in this book, together with another fave of mine, Vlad Dracul, that it might have qualified as part of the Night Huntress World book. Still, it was nice to see the new, changed Mencheres with his true love, the changed, more humble Mencheres towards Cat, having made peace with both her and Bones. Vlad provided some instances of laughter and I hope that he gets his tale soon.
I'm not going to give too much away, other than that a main character dies...but not truly, Justina has turned into a kick-ass fighter type, wanting to avenge her dead love Rodney the ghoul, Cat and Bones have to battle an enemy who is sometimes a friend who could and does turn into an enemy in the blink of an eyelid, and at the end, we see some changes to the team. In fact, at the end of the book, we get to see a preview of the next book due out late 2011 (in which the dead character appears, so I'm not really giving anything away) with a new boss taking over the team and making waves with Tate and Cat.
A major plus for this book IMHO is that once again, we see the romantic side of Bones the killer, when he misses Cat who's had to go undercover. They actually spend still quite little time together, but the way in which each `reads' the other, and what each is prepared to do for the other, and to protect the other, makes theirs a true love story. Watch out for the scene in which Cat avows her love for Bones and the scenes - at the same time funny and highly erotic and lengthy - when a change forced onto Cat turns her into a nympho. Boy, scenes to rival an Ellora's Cave novel!!!
Overall, good, but not great, but still an autobuy for me.