This is one of those few games where you perceive that development teams poured a lot of effort and heart on it. The story is very related to human nature, which makes you think while enjoying this 6 hours long journey. This is a puzzle game style, it has hard part but it is mostly challenge enough to make you enjoy the game without any frustration.
The hard part is to find all the secret, I think that to get 100% of the game, several plays through have to be done. I only got 47% of the trophies especially because I got slightly more than half of all the secrets.
Trophies actually reflex your efforts. It is not the kind of game that you spend 50 hours and only get 30% even getting to the very end.
Graphics: it is really beautiful. It uses a very well develop technique that make you see 1080p 3D image. Especially with the environment that they chose.
Sound and music: top notch, it is not the best I heard but makes the journey more pleasant and strengthen the attachment with the game.
This is a game that you have to experience. Not for everyone but worth the try.