LOVED this book. It had it all for me. Set in London. Strong historical element (the history of the Jack the Ripper murders). Great cast of believable characters. Grisly murders and exciting chases. Strong procedural backbone to the plot. Gothic elements abound. Cinematic set pieces create lots of drama. Even got extra points for bringing in social issues that impact Londoners of today.
Plotwise--someone is mimicking, which is different than duplicating, the Ripper murders. More of an homage than a copy cat. You have to really be on your game to anticipate their next move. Lacey Flint is as damaged and perhaps as dangerous as the criminal that she pursues. Constant left turns and plot reversals keep the reader fighting their own preconceptions as theory after theory blows away. Eventually I just enjoyed the ride, stopped trying to figure it out, and had a great time.
Then I sat back and thought about how much fun I am going to have reading the rest in the series. From what I have read here from other reviews, they get even better, which is definitely saying a lot considering how much I enjoyed this one.