Beating Fez isn't puzzling... you can go through it minimally and just get the obvious cubes.
But if you want to play the game right... there's TONS of puzzles. There's an alphabet and numerical system to decipher. The in-game clues are cryptic and not so obvious (until you figure them out... then it's like "oh yeah!").
It's the first game I've played in years that I actually had to bust out a pen and paper to take notes to figure it out. It's crazy.
On top of that the game itself is creepy/surreal/trippy. The game is a total mind warp.