I am two episodes before the end and I think this drama is excellent. It is not a thriller drama but rather a filmed profiling textbook where the main aspect is not running after a wanted man with a gun in your hand but a tedious, time-consuming investigation that often leads nowhere and the case is solved by... chance. This is an intelligent drama, showing many psychological aspects of the criminal but also of the policemen who have to deal with brutal, nightmarish crimes whose cruelty is beyond human comprehension. It is not a thriller, not even a crime drama, it is a brilliantly filmed struggle of normal people who look into the abyss every day not to fall into it.
I've been waiting for a drama like this for a long time, and with two episodes to go, I'm completely satisfied.