Fire up the portal gun and take a copy home
Having been a fan of the original Portal game this purchase was a must have for me. Very rarely do you get to play a game which actually makes you feel clever when you go through the challenges. Stephen Merchants voice acting in this is genuinely laugh out loud and the return of GlaDOS is great too.
If you haven't played the original I would advise you to purchase the first one just so you can appreciate the story and it will also act as good training for this game, the first one can be found as part of the "Orange Box" Half Life 2 pack or can be downloaded from Xbox Love "Portal - Still Alive".