Scariest, most stressful game I have ever played.
If you grew up with classic franchises like Silent Hill or Resident Evil when they were still good, this game takes it to a whole new level. In fact it's pretty much the only fairly recent survival horror game that exists as even Resident Evil has sold out and become action horror in the quest to make more profit.
What makes Amnesia work is that the game has a perfect atmosphere and presentation. Spring loaded cheap scares are few and far in between and the fact that your adversary (a dark force is the only way I can describe it) chases you throughout the game cannot be killed but can easily kill you. Your only weapons are matchsticks that light your way, getting good at slamming doors on the darkness, or finding a good hiding place to crap yourself in. Hope that it doesn't find you.
The people who developed this game did a really good at pacing. After an intense moment with the darkness and barely escaping, the game gives you a short break. Usually during this time you are given a puzzle to solve to move past the next obstacle. But even during these moments, the game will often give you a false sense of security and the worst things will happen when you least expect it such as having to run through a basement filled with water while being chased by an invisible being. Or trying to open a stupid gate with the invisible being right behind you only to realize that you have to manually open the gate and if you let go of the wheel, the gate firmly shuts again requiring you to repeat the process.
If this game has one fault, it is not very fun to play because it is too damn scary and stressful. You're always on edge because the darkness could appear at any time. There are rarely rooms that are safe. I give this game a 10 because it succeeds to the fullest degree in what it intended to do and I cannot think of a single thing I would change.
If you want to play this game I recommend bringing a few friends and drinking lots of alcohol. I think it sucks that this game doesn't have an achievement system because it really only needs one achievement and that is beating it because that is an accomplishment in itself.