Amnesia: A Machine for Pigs Review (Tehlster)
I think it's best for me to look at this game for what it is rather than what it isn't. Is it an Amnesia game? Yes. Is it better than The Dark Descent? No. I understand the gripes people have with this game, many of which are valid criticisms, but I do think this game does set itself as a unique experience.
It's missing a lot of the mechanics that are present in The Dark Descent, the enemies aren't all that challenging or scary, and the game is short (for my first blind playthrough at least). However, the game does shine in it's environments and story. In both regards, they are excellent contrasts than what is present in The Dark Descent.
If you're looking for a different, unique experience and story for the Amnesia games, then I would recommend this game, but you don't need to play it to get the full understanding of the Amnesia universe. Just be sure to get it when it's on sale.
If you do play it, I recommend turning anti-aliasing (or smoothing in-game) and ambient occlusion off. According to some people, having these settings on can drastically lower framerate while providing little improvement to visuals.