This is one of the best TV shows ever made. There are almost no weaknesses, from the storyboarding to the directing, animation, and voice acting. It is all amazing artistry. Like Game of Thrones or the Kim Stanley Robinson Mars trilogy there is no true protagonist, nor point of view characters, but there are key relationships (such as sisters Powder and Violet, or research partners Jayce and Viktor) around which everything else revolves.
There is incredible world-building, but miraculously without tedious exposition. The world speaks for itself by making the characters react to it.
All you need to know going in is that the upper city has profited for centuries from the same disaster that left the lower city in squalor, and never used those profits to fix the problems in the lower city.
The animation is by a French studio that previous to this have mostly been making promotional material for the game this show is based on. Make no mistake, this is some of the best animation I have ever seen. Riot Games must have spent a lot on animation. The animation is so good, and the facial animation involves so much subtlety that many mistakenly assumed that motion capture was used. It was not. The stress and madness of one particular character is represented visually in a manner highly reminiscent of Bill Seinkeiwicz's art in Elektra: Assassin. Another character has a peculiar leg shake whenever she gets stressed. The details in the art and animation are incredible.
The voice acting is top notch, and includes major talent delivering stunning performances. The actress playing a certain little girl will crush your will to live in episode 3.