Book lives up to title. Read it expecting that almost anything, no matter how much of a constant it's been over the past eleven books, might be altered, revised, or destroyed. Any given plotline you've been waiting for Butcher to move forward or develop, there's good odds you'll find out more here, and more than one multiple-book plot thread finds its end.
Butcher is at the top of his game here, and it may be the best overall book in the series to date; from the very first line -- "I answered the phone, and Susan Rodriguez said, 'They've taken our daughter[,]'" -- the book moves at a page-tearing clip, and I read it pacing back and forth in my living room, so wholly and obviously absorbed that my girlfriend gave me the night off from household chores ("Sorry I haven't done the dishes, dear. I can't. Book." "I know. It's okay.")
Butcher's spent the past eleven books developing Harry's character, establishing his hunger for family, his devotion to saving innocents, especially children, and his willingness to burn the world in order to do the right thing, regardless of cost; he's also balanced Harry on the knife's edge of several different horrible temptations, and shown that Harry's passion has the potential to lead him very badly astray. This book drops Harry onto that knife edge and then hits him with a truck, and much of the tension in the book comes from watching Harry discover just how many moral and emotional lines he is, after all, willing to cross, and how many irrevocable steps he's willing to take, in order to save his daughter.
It isn't unrelentingly dark; the trademark humor of this series is on display, and fans will find plenty to chuckle over in between the explosions (my favorite, among many, might be Harry's pointed refusal to wear a hat, a subtle comment on the inaccuracy of the series' cover art). Despite that, though, this is definitely the psychologically darkest book in the series so far, and I expect it marks a trend we'll see continue in later books (Butcher plans to write approximately 12 more books in the Dresden series).
Like many a season finale, this book ends on a bit of a cliffhanger -- while the plot of this story's resolved, there's a 'Whoa! what just happened?" moment on the last page or so. The good news is that the Dresden Files short story anthology,
Side Jobs: Stories From the Dresden Files includes a novella (titled "Aftermath") set forty five minutes after the conclusion of this book. The bad news is that "Aftermath" doesn't include any direct answers, just a few more pieces of the puzzle, so we'll have to wait for the next full novel,
Ghost Story , for clear resolution.
I don't recommend starting the series here; start with the first Dresden Files book,
Storm Front, or with the prequel graphic novel
Welcome to the Jungle, and work your way forward. If you'd like a preview of this volume, though, the first four chapters are available for free on the author's website.