"A sad but beautiful game" - this is how I described it to anyone who asked. Even though you play from the perspective of the villains, as a player I was compelled to keep going so that I could get every bit of story, which is strangely hopeful in its way - though the final context of it wraps that hope all up in an immense but relatable tragedy.
The concept of only having boss fights is a stroke of genius - each one is more like a difficult but fair puzzle to work out. And the realization towards the end that each monster represented a person whose memory is desperately trying to save a strong, kind personality from being erased is one of the best twists I've read in anything, ever.
It's clearly a labor of love and though I originally found the whole concept very intimidating on approach, the game itself is so artfully crafted that it drew me in and the emotional gutpunch makes for a perfect catharsis.