Pros: Amazing audio-visual elements, varied gameplay options
Cons: Somewhat limited replay value
The bottom line: A genuinely impressive FPS with great atmosphere and intriguing gameplay options.
Imagine a world where the 1950's led to a revolution in technology. A world where the capitalists and commies were rejected; where a courageous man by the name of Andrew Ryan built an underwater city where the "enlightened" members of the populous could flourish, helping to usher in a new era of wonder....

Until, of course, the people realize that their technological advances come at the price of harvesting genetic material from little girls called "Little Sisters" guarded by heavily armored guys in diving helmets known as "Big Daddies". And, of course, said genetic material will progressively drive the citizens of Ryan's wonderland, Rapture, completely insane, to the point which their addiction leads them to attacking, well, pretty much anyone.

Essentially, that's the plot of BioShock, largely a spiritual successor to the classic System Shock 2. You're some dude that inadvertently winds up in the hidden, underwater city of Rapture, the brainchild of an exceptionally John Galt-esque character named Andrew Ryan. Everything has gone to hell there, and some dude named Atlas wants you to help out in getting rid of the problem of that damned Ryan dude.

Which is really only the tip of the iceberg in this wild and crazy game. By the standards of first-person shooters, this is not exactly the longest-playing game; it has no multi-player features, after all.

On the other hand, there is a pretty impressive level of gameplay options. While the standard issue list of "smacking weapon", "pistol", "shotgun", "machine gun", etc. is present, there is also a set of unusual abilities activated by the left trigger, known as "plasmids". Varied as they may be, there isn't necessarily much practical value to utilizing said plasmids.

Still, it is pretty damn cool to attack people using attacks that electrocute or immolate someone.

The game is largely quality; easily, the best feature of the game is its sheer immersion factor. It is remarkably hard to distance yourself from the action on the screen; the amazing visuals and absolutely gorgeous sound suck you in like few games I've ever played. In fact, I found the game hard to play for long times because I was, frankly, freaked out a lot by the atmospherics (the combination of period music, creepy little girls and the potential that someone will attack at any moment makes for a harrowing experience).

The story is solid too, up to a point. The tale is told in bits via Atlas' narration and audio journals found throughout the areas of the game.

However, at a certain point in the game (if you play the game, you'll recognize it), the game turns into a standard "find the widget, find the next widget, find the next widget, etc. till you meet the main boss" first-person shooter. The game experience is still quality, but the story loses a little for it.

Other elements of the game are minor, but still interesting. You can hack machines that appear in the game (flying attack bots, security cameras, vending machines that you buy ammo and life boosts) and make them help you by playing a "Pipe Dreams"-like game. You can also invent things at "U-Invent" stations by collecting various odd objects.

You can also buy the aforementioned Plasmids and power/ability upgrades called Tonics. These genetic upgrades (gene-splices, as the game calls them) are purchased at Gatherer Gardens, and are bought using ADAM, the material you harvest from the Little Sisters after dispatching of their guardian Big Daddies. One of the more unique gameplay elements of BioShock is the Little Sister dynamic; to wit, you can rescue them for a little ADAM, or kill them to harvest a lot. This, combined with the variety of Tonics in the game, offer a lot of customization.

As I mentioned before, this game is one player only, which does limit the replay factor quite a bit, but it does partially ameliorate this by having a slightly longer than usual campaign mode; as well, the variety of ways you can use the Plasmids and Tonics could make the game play a lot different.

For instance, I mentioned before my general disuse of the Plasmids; however, others I've talked with used them heavily. On the other hand, my generally impressive puzzling skills meant I would hack pretty much anything. The variety of approaches to situations is pretty impressive (for the first 2/3 of the game, anyway).

All in all, this game is an incredible testament to the technical abilities of modern video games, on top of being a highly entertaining-to-play first-person shooter that's more than a little freaky.