More crime fiction than mystery. Less whodunnit and more how-they-get-him, but that doesn't have quite the same ring to it. In this author's capable hands it works though. There's a tension to proceedings that grips you (will Street get got? how will they get you-know-who?) and the author uses timeskips effectively to trim the page count. The end result is a taut, well-paced crime noir book. This is something I am coming to appreciate more and more especially as an antidote to the sometimes bloated epic fantasies I read. We don't need all the details, the timeskip with enough information and motivation for characters can help fill in the blanks. In this case it leads to a great chapter with Harpur being cross-examined in court regarding his obtaining of evidence, with almost all of it being dialogue so it zips along. Speaking of the dialogue, which is a real highlight, it feels authentic, helps differentiate the characters and adds some much needed levity to the book. None more so than Iles who makes you wonder how he gets away with saying the things he does especially to people further up the chain of command. On the other hand it's worth mentioning that the dialogue references people and places from the UK in the 70s and 80s, features heavy use of slang and so might make it more difficult for non-UK readers to follow. I had to google some of the things mentioned.
Highly recommended for fans of crime fiction.