This book was excellent. It is the twelth book in the Harry Dresden series. Without giving away the whole plot, I'll basically say that in the first book, Harry Dresden, Wizard for Hire, had a dark cloud over his head. If he screwed up, the Wizard Police, in the form of the Warden Morgan, would kill him.
Turn Coat begins with Morgan showing up at Harry's door seeking protection from the same Wizard Police. Harry has to solve the murder in a classic whodunit with supernatural elements. There is also a lot of intense action.
One begins to wonder if the plethora of supporting characters that Butcher has slowly been giving Harry are all going to be maimed, mauled, stolen or killed. Good fiction often involves the suffering of the primary character, and hitherto now Harry has suffered a great deal, but he has also steadily advanced in power and had a circle of friends he could rely on. At the same time, many of these allies are becoming tainted or harmed by his mere presence, such that he might not have an allies by the time the 20 book series is done.
Which, as I said, tends to make good fiction as long as it is done properly.
I also think that this book may represent the last of the books that follow the standard formula of "something horrible shows up to Chicago, Harry finds out about it, Harry ties to fix it, Harry gets not just one problem but four or five and somehow manages to come out on top with some consequences that last a few books." The title of the next book is "Changes" and I think that the stage is finally set for the ultimate conflict with The Black Council.
And I'm looking forward to it.