This drama is extremely good, the storyline itself is truly intriguing, the acting was really good, the ost,visual fx-a job well done, need I say more. I am currently re-watching the drama. You won't get disappointed, give it a try. I mean I have seen worse and I am wondering why other people gave a low rating. I almost didn't watch it because of all the negative reviews and comments

Acting:
From the main actors to the smallest roles everyone did a good job. The main actors had good chemistry.

Storyline:
I am not sure why people are getting confused. It's not science rocket, the narrative is that there is a parallel world and has similarities but slightly different that's it, very simple to understand.

All in all what i am trying to say is that the drama is really good.