I'd put Kari (our protagonist policeman) somewhere between Monk and Sherlock and possessing the usual Asperger tics.
It's great fun, atmospheric, and dark—just like a gritty Finnish cop show should be.
As you can imagine, Saint Petersburg figures prominently, along with the mafia and all their excitement.
p.s. Having finished every episode now, I mourned a bit when it ended! I loved how the series came full circle, depositing each character in a significantly different place than Episode 1. Very well done...and successfully, cleverly pre-meditated.