This drama is sadly underrated. The acting of the male lead, Jung Kyung Mo, is great and its shown through his perfect submersion within each scene's "genre". The show has thrill, mystery, and even frustration because of the situation the characters has to deal with. However, it doesn't mean it's bad. You care for the characters and there are twists and turns.
With that being said, the drama has their good share of comedy as well. I believe most was done as ad libs from the actors themselves.
Be warned, it's almost like Game of Thrones where your favorite charcter may die.
However, because of its comedic yet dark twists and turns, it is really enjoyable to watch.