I don't give five stars easily, and I could argue that this book isn't a true five star book by my usual criteria, but I think Mick Herron's work is way, way, better than the ratings and reviews it's getting and I'm rating it a total five to bring up the ratings.
Now, I'll admit, I like slow, noir, complex stories, and pointless sex and graphic violence is a complete turn off, so if in your ideal mystery someone has to die in an explicitly gory manner or get laid every few pages this stuff isn't going to work for you. But if you like tight, well plotted stories with complex, interesting characters, nicely crafted suspense, and superb dialog you really should give Herron's work a try.
I don't think I'd claim Herron's novels are perfectly written, but they hold together as well as any of this sort can, the plots don't suddenly become fantastical or insulting, and your heartstrings aren't yanked by some mawkish character. In my opinion he's in a class with Le Carre, or Martin Cruz Smith and really, I think a better writer than Nesbo.
If you try any of the Slough House series, pay attention! Herron has a fantastic, dark sense of humor and he exercises it beautifully, but it's subtle enough, or I'm dense enough that sometimes I'm a sentence or two away before I realize what just happened.
I'm working my way through all his books and will be sorry to complete them.