A wonderful game that really pulls you in.
The obvious high-point that everyone mentions when reviewing this game is the story. It's communicated in large part through disembodied voices who portray their lives and struggles via many different tape decks you find lying around the large and unique levels. The voice acting is top-notch and really makes you wonder who these people are and what has gone so disastrously wrong in their city, Rapture.
While the game takes place in an underwater city, the variability of the art design (which is largely reminiscent of 1950's deco) heavily influences what you see: repetition is not one of this game's weaknesses. From large concrete rooms full of thumping and humming machines to frozen hallways to run-down living quarters that are dripping from the leaks that so threaten Rapture's existence, simply walking around and enjoying the scenery is a treat enough in itself.
As far as the game play goes, some might say it's deceptively simple. You can crouch, fire any weapon in your arsenal, or switch to your plasmids. Plasmids are upgrades that grant you abilities ranging from the power to throw lightening bolts to shoot a swarm of angry wasps out of your hands. Yet it is in these powers that many say the game truly shines: While anybody can hold the trigger on the automatic Tommy-gun that you find in the game, it's much more satisfying to mix and match your freezing ability with the concrete sound of your wrench smashing a frozen human form to thousands of pieces.
In some ways, I would consider this videogame a book. Not because of a lot of reading you have to do (there isn't much at all) but rather in the form of really pulling you in from your immediate surroundings, and making you desire to push on, to really conquer your foes. It becomes a game that you are not playing, but rather are a part of. And in any case, a quality like that earns an exceedingly high rating from me.