Are you one of the few that have yet to explore the world of Rapture? Amazon is running a secret sale that lets you score both BioShock 1 and 2 for only $50 -- less than the cost of BioShock 2alone. To take advantage of this deal, you'll need to add either the PS3 or Xbox 360 versions of both games into your shopping cart; the discount will appear there. (Sorry, the deal isn't applicable to the PC or Limited Edition versions.)
Starting with this combo bundle will give you the rare chance to play the entire BioShock saga in the correct canonical order. Remember to start with BioShock 2's multiplayer mode, then move onto the original BioShock, and finish with BioShock 2's story. That's the only way you'll get the real experience.