In short: I loved it and would recommend everyone that likes a bit of fantasy romance to definitely give this a chance.
Long review: (Might contain spoilers)
Story and the concept- I am not a big fantasy watcher but I loved the whole concept of the doors and the world-building inside every door. I came into the show completely blind but the themes and stories inside the doors blew my mind especially the fact that they were based upon various cultural legends and tales. I would have to admit that the 10th door was my favorite. All the doors were incredible and instantly pulled you in. I really liked the way the show brought the book to life.
I started with the show but then midway decided to read the book too as I wanted to learn more in depth about the rules of the doors ( as they were sometime not explained very well in depth in the show).
In the show my personal favorite part was that they made LQS's characters more special. Even though everyone in the book (mainly RNZ) always said LQS was special, him literally solving the door ghost's problems and being just a kind guy really made the character extra special and endearing for me.
Therefor, in the context of the cinematography and the story adaptation I feel the drama did a very good job. Better than I could have imagined. I loved the little twists and extra storylines they added for some door ghosts and side characters. (One of the biggest example the father of the triplets from the second door).

Acting: I was not familiar with any of the actors before this show but they were all pretty watchable and according to me played their roles really well. Some actors (like the twins) did a great job. Especially towards the end of the show.

And since this is a censored version there was not too much chemistry between our main leads at most times but you still get the feels in the longing stares (from RNZ). Since I was reading the book while watching the show, it really helped fill in the gaps in terms of the close-ness between the leads. So in my mind it wasn't lacking too much but yes their relationship not very explicit in the show.

Thoughts on the ending: While they I loved some of the changes they made in the show from the book, there were definitely some that were a bit questionable (SPOILER ALERT: THE ENDING). I fell in love with the ending of the book with RNZ and his arc as the 12th door. I cannot express in words how the ending made me feel. Like WDYM RNZ was LQS's 12th door - his heart's calamity. Therefore I was not the biggest fan of the ending of the show that not only made the whole adventure of the doors a sort of hallucination for LQS also made him seem like this slightly crazy guy who spent 50 years of his life trying to get back a 'virtual group' of friends, never actually living a decent life in the reality.
But I like to think of the endings of the book and the show as a pair of parallel universes where in one universe RNZ gave up the 'virtual world', his whole identity, to stay forever with LQS in the real world and LQS spent his whole life and gave up on the real world in order to create a virtual world where RNZ is exists. If I had to make an edit about them, I would use the song midnight rain by Taylor Swift.

OVERALL: Its unlike any other show that I have watched before and I would definitely recommend every one check this out. It is not a show you would regret clicking on. It is very well made and you can feel the hard work the crew (on and off screen) have put into it. It kept me entertained throughout the episodes and I do not remember a moment that I felt was filler or irrelevant. In contrast I would be willing to watch these cuties go through many more doors. The writing was very strong in the first 90% of the show and it kind of starts going downhill towards the end (where they stray from the book) but still an enjoyable watch.