1 word: LOVELY.
This game truly is a piece of art, the most charming game I’ve ever played. The artwork is gorgeous and simulates a surreal, detailed world in an atmosphere similar to France in the 1920's. The soundtrack is also amazing and fits the game and environment perfectly. Contrast is overall quite original, from the shadow-shifting between two different worlds to the special artistic style.
It takes about 5 to 6 hours to complete. You could think this is rather short, but the delightful artwork really makes up for it. This game really is a story-driven experience, so if you're not into this, maybe this isn't really the kind of game for you.
I really like the story and the characters. They did a great job on the voice acting. The story is touching, lovely and well thought out, kind of mysterious due to the two different worlds. In the end, I still don’t really know which one’s “real” and which one isn’t.
The puzzles are special because of the shadow-shifting mechanism. Each puzzle is different, fun and challenging, not repetitive in my opinion.
Sometimes the game's a bit buggy, like the shadow-shifting mechanism between 3D and 2D at certain moments. The camera can also be a bit buggy and clumsy sometimes, but it doesn’t ruin the game.
Something you need to know: you can't change the controls. The game works with a QWERTY-setting, so keep this in mind. You can also play this with a controller, which I think suits the overall controls better. I still have to try this, though.
If it’s in sale, buy this immediately. Totally worth it.