If you don’t care how much evidence you leave behind, or what ending you get, you could probably beat the game in under an hour. If you play the game “properly” instead of being sloppy & speed-running, I think that a play-through could last up to 10 hours. If you try to find every collectible, max out every skill, earn all Achievements, and obtain every ending, then you might spend at least 75 hours playing the game.