One of the best games. Period.
At a glance, Braid appears to be a simple puzzle/platformer with a time-bending gimmick. Some might call it a Mario Clone, but those people have not played past the first world. There is a point in the game where it just clicks and the players realizes how great the game really is.
The "story" of Braid is very strange. There isn't really one "story" to the game. The message of the game can be interpreted in many ways. The simplest being that there is a princess needing rescue and the most complex (so far) theory involves (spoilers?) Nuclear Weapons of all things.
There is not much else to say. It's an amazing game. The puzzles are complex and varied, which is surprising since you can only manipulate time. The developer really utilized that mechanic to it's fullest extent. Go buy this game