The structure of the story and the way it's told is genius and could only work in a video game.
13 Sentinels means there are 13 characters and 13 stories.
Most of one characters story is somehow connected to the story of another character while also telling one big sci-fi story. So to understand one character, you have to play all the other stories.
There was not a single hour in my first 20 hours playtime (in total about 35)where there wasn't a major plot wist or event that changed my whole understanding of the story or a character. The story itself is one of the best sci-fi stories I have experienced yet. Almost every sci-fi concept you can think of is in this game : time travel, aliens, big titans (sentinels) ……
The backgrounds are beautiful paintings and the OST is fitting.

There is also a whole RTS game mode. This one is nothing special and really easy. I enjoyed how easy and satisfying the fights were.
They are good enough and a welcoming opposite to the standard game where you mostly listen to the story and do some little riddles

If you want to experience a unique sci-fi story, play this game.