What is so fascinating about this game is that it is different. The vast majority of video games these days require hand contortions to get all the "moves" right. Limbo requires two buttons - jump and apply - and one joystick since the action takes place only in two dimensions.
And when most video games are trying their hardest to cram in as many realistic effects as possible, Limbo is minimalist, using only gray scale. Your character is hidden in shadow with no features, only the reflection of his eyes visible.
Most of the game I would classify as "puzzles" as you try to figure out how to keep moving forward. As you descend further and further the scenery gets weirder, the opponents scarier. And with the minimalist monochromes and strange images, the tension and the weirdness of the world just goes up as you keep descending.
I highly recommend this game, but not for small kids, even though the controls are simple enough for them.