Extremely immersive and scary
This is a scary game, and not in the cheap monster-in-the-closet kind of way although there is the occasional moment like that. Amnesia's scares don't come from just it's grotesque monster design, it's a lot more focused on it's sound which create a menacing atmosphere for the gloomy backdrop. The main scares from Amnesia instead come from the feeling of total helplessness. Monsters will hunt you in the dark cold corridors of the ancient castle and you can do NOTHING about it except hide and pray to whatever gods you believe in that you don't get caught. With no way to fight back, this creates one of the most tense experiences I've felt in a videogame before.
The horror is backed up by a surprisingly interesting story to boot as well. It all starts with you waking up in a castle with no recollection of who you are or what you're doing, you're only clue being a note that was written to yourself saying that your name is Daniel and you need to kill a man named Alexander who lives in the deepest part of the castle. The story is then further added to in fragments through notes scattered around the castle which eventually piece together the larger picture, with some truly gruesome revelations in the late portion of the game.
Besides the horror there are also plenty of puzzles to wrap your head around throughout the game. The solution to the majority of these puzzles are quite logical however some take a bit more scanning about rooms trying to find that one last vial you need to make that damned potion! This can remove some of the immersion from the game as you frantically search around and around in frustration to find one little thing. Overall, not a huge issue though.
My only other real issue with the game is that the ending is a little weak. I can't really say much without spoiling it but it seemed to end quite abruptly to me.
All in all, I couldn't recommend this more to someone who loves horror. This is probably not for the faint of heart though!