My least favourite of the series so far. While I'm writing this review I'm actually considering lowering the grade to two stars; only the last chapters do a great work of redeeming a book that was on so many aspects disappointing. 
 First of all the chapters told from the killer POV: a huge failure. They sounded fake, evil in a childish way, their only merit being that Rowling actually manages to scatter ambiguous information that confuse the reader on the true identity of the killer, who, until the last chapter, could easily be any of the three men Strike suspects. 
 Then there are the long, long, long parenthesis devoted to the characters' introspection. I like to know more about the characters' feelings and past history, especially when concerning the two protagonists who, as shown in the two previous instalments, have proven to be interesting and appealing. However Rowling here seems to lose herself in these digressions, which are often a bit repetitive and sometimes disjointed from the main plot (even if the brutal killings are what originally triggers these walks down the memory lane). 
 Finally, the mystery here is solved mainly by spending long tedious hours surveying the dwellings of the possible suspects, without a clear clue of what should be done in case one of them would actually show up. This leads to a series of repetitive, boring chapters where the Robin and Strike do nothing more that bide their time and dwell on their past. 
 I actually enjoyed learning more about Robin and the up and downs of her relationship with Strike were definitely entertaining but, if not for the several coup de theatre of the final chapters, I would never have given more than two stars. I appreciated the exploration of the theme of violence against women and Rowling effective description of how victims are often shamed by the press and by the the defenders of their assailant, a pratictice too often seen in everyday life unfortunately. There are also sequence of good mystery thrown here and there but on the whole there are too many weak points and the prose sounds forced, rehearsed, victim of too many stereotypes. Plus a serial killer who repetitively stabs his victim and five minutes later manages to board a bus without attracting attention having only his finger dirtied with blood is absolutely unbelievable.