Firstly, this is based on an award nominated, highly regarded horror manga. I haven't read all the manga, but I did dip into the end of it to try and get some explanation, and the end differs significantly, but the main characters are instantly recognisable.

I can honestly say that I have never seen anything like this before (and I doubt if I ever would on the BBC), but it is not my usual genre, so for all I know it could be run of the mill typical fare.
The characters are extreme caricatures, the plot veers from slapstick comedy to extreme violence, (including sexual violence) and jaw dropping craziness, made worse by the main characters acceptance that this is somehow normal.

Hoshino Mari is excellent and unrecognisable in her role of the belittled abused sidekick, who nevertheless is a tenacious detective, she looks just like her manga counterpart and plays the Stan Laurel to Tayama Ryosei's obnoxious, misogynist & abusive Oliver Hardy (he is also just like his manga counterpart). Takahashi Issei does a good job as the local Policeman out of his depth. The minor cast do a good job of projecting an aura of creepy malevolence behind a happy facade. The atmosphere struck me as 1950s Americana with the tv jingles at the end of each episode and Happy Valley vibe.

Did I like it? Not particularly. It was good enough that I kept watching trying to figure out what was going on, but I was left disappointed that there was only a superficial theory, and a lot of loose ends (I'm not a fan of films/dramas where you have to go to discussion groups to try and make sense of what happened, I like my endings unambiguous and obvious)
It wasn't sufficiently thought provoking that I spent time afterwards trying to puzzle it out, and it didn't give me nightmares!

The general consensus seems to be that Twin Peaks fans (a series I really didn't didn't like, or watch beyond a few episodes..) will love it, maybe this is true...