For both rich atmosphere and unique game mechanics, you could do a lot worse than Return of the Obra Dinn.
If you're unfamiliar, the presentation evokes early PC (or Mac, more specifically) black and white "1 bit" games, but real time 3d. This already is very distinctive, but the gameplay also sets it apart.
You are an insurance investigator with a magic pocket watch which allows you to travel back to the moment in time that someone expired, if you find their corpse. From these brief flashes (and by cross-referencing the ship manifest) you piece together what happened to all the crew and passengers on the ships ill-fated voyage, before it's baffling reemergence years after the fact.