This game deserved far better sales than it got. Like Beyond Good and Evil, it is an excellent game with fairly standard gameplay, lots of character, an entertaining story, and a fantastic style all its own, but it never met with much monetary success. It's a crying shame.
The gameplay is a lot like what would happen if you took the Legend of Zelda series (from OoT on) and made it so Link could jump on command. You get several additional abilities that you can map to the controller buttons (or keys, if you're stuck with the keyboard), and have to switch between to deal with different situations. Nothing really new here.
The game's environment, however, is a breath of fresh air, and makes the game one of the few brilliantly original pieces of gaming made in the last twenty years. The gameplay doesn't get in the way of your exploration of the wonderfully insane worlds you come across, and that's all it needs.
If you utterly loathe 3D platformers, you might give this a pass as it is likely to cause controller-throwing frustration. Failing that, however, you have no excuse to not BUY THIS GAME BUY IT NOW NOW NOW WHY AREN'T YOU CLICKING BUY INSTEAD OF READING THE REST OF THIS REVIEW.