This is book 12 in the Women of the Otherworld series, and while Kelley Armstrong's books previously have been pretty stand alone from each other, this one will make little to no sense unless you've read at least Waking the Witch, and preferably also Personal Demon, No Humans Involved, Broken and Haunted. So there will absolutely be spoilers for the previous book. If you haven't read it, skip this review, and go read Armstrong's back catalogue instead. It's pretty much all excellent.
Savannah Levine, daughter of a very powerful witch and a sorcerer, has lost all magical ability, and is unsure of how to handle herself, having always relied on her magic in all aspects of her life, especially when working for her guardians' investigation firm. There's a witch hunter after her, who doesn't realize that Savannah is powerless now, and Savannah wishes she'd paid more attention to traditional self defence and investigation technique. Her various supernatural friends cannot find a reason for her sudden loss in powers, and once it turns out that the witch hunter is the least dangerous of the ones wanting their hands of Savannah and several of her friends, she'll need to figure out how to get her magic back, so she can help out in what looks to be a supernatural war.
Savannah has been a supporting character in several of Armstrong's earlier books, and got her first "starring role" in last year's Waking the Witch. While she's 21, Savannah is also self-centered, immature and quite annoying at times. Considering the very privileged life she has led, she should be a lot more grateful, and less of a spoiled brat. This is clearly intentional, as Armstrong has not one, but several other characters tell Savannah to get the heck over herself and start growing up in this book. Which she appears to be doing, with minute baby steps.
For long time readers of Armstrong, this book pretty much features every single character who we've met in her universe before: Elena, Clay, Jeremy, Jaime, Paige, Lucas, Cassandra, Hope, Karl, and of course, Adam. Most of them have little more than cameo appearances, several of them feature much more prominently in Industrial Magic, for example. Still, this story is clearly mainly about Savannah, and her development into one of Armstrong's strong and admirable heroines. This book is clearly also the middle installment in what will be a trilogy. It starts immediately after the end of the previous book, and ends with most of the threads introduced in this book unresolved. According to the internet, the concluding book, not just to the trilogy, but to Armstrong's entire Women of the Otherworld series, will be out next year. As someone who's followed her series for nearly a decade, I will be reading that one as well, even if this was one of the less engaging of the installments.