This review is a strictly enforced spoiler-free zone. It's vital that you don't let anyone spoil BioShock for you, and three words would ruin it. So kindly refrain from reading any forums and the like until you've bought, played and completed the game. Which is something you should do as quickly as possible. Partly because it's a wonderful game, but also because I'm not sure how long I can go without talking about the bit where (spoiler deleted. Sigh. - Ed).
Some of the things that make it so extraordinary are things I can't tell you about without spoiling them, so this review is going to be about the ones that I can. All I'll say about the premise is what they'll probably put on the back of the box: it's 1960, you're on a plane, and it explodes over the ocean in the middle of the night.
It's a spectacularly beautiful opening, from the moment your head breaks the flame-glinting surface of the oil-black water with a spluttering gasp, to when crackly violas groan out a quietly mournful fanfare to your first glimpse of Rapture, BioShock's underwater metropolis.
It was supposed to be a refuge, where brilliant minds could free themselves of the burden of lesser ones. But geniuses are not well-known for their psychological stability, and the extensive self-modification possibilities of their stem-cell technology - 'Adam' - freed them to inflict their delusions and neuroses on themselves. What's left of their utopia is a dripping ghost city of mutilated, murderous freaks. It's one of the most extraordinary places I've ever explored in a videogame.
Once there, you're led through the game's unusual fundamentals: a wrench to hit people with - familiar enough - and a Plasmid. Plasmids are Rapture's techno-magic, and they tend to immobilise, weaken or trick enemies rather than kill them directly. Mixing them with the game's more conventional weapons is a magnificently creative and violent process.
You're also introduced to hacking, the system by which you can befriend any turret, drone or security camera by, er, playing a mini-game identical to Pipe Mania (snipr.com/pipem). Whatever the logic may be, it works: it's tense, stressful and fun. I had my dictaphone recording as I played and at one point you can hear me saying the word "F(lip!)" 26 times during a single hack.
One of the game's more radical quirks, however, isn't obvious until you die. You can't. When you run out of health, you emerge from a regeneration chamber with the game world exactly as you left it. It's a brave and ultimately successful ploy to reduce frustration when you're starved for resources. It elegantly renders quicksaving - the more intrusive way of achieving virtually the same effect - obsolete.
If you're not dying, fighting, taking pictures or playing Pipe Mania, you're probably shopping. BioShock deploys almost all its RPG elements through vending machines, as odd as that sounds. From them you buy Plasmids, their passive cousins, Tonics, and extra slots for each.
Plasmids are essentially spells, so more of them means more options in combat. Tonics are as near as BioShock gets to attribute boosts, in that they improve you character's capabilities, so a few more of these essentially constitutes a level-up.
But one of the reasons this system is so smart is that it's not as simple as that. For one thing, you can switch your choices out freely at Gene Banks all over Rapture, so there's masses of room for experimentation and variety. And because Tonics aren't restricted to dry numerical increments, they get wonderfully exotic. To give you some idea of how distinctive you can make your character with these, I focused my character so tightly on hitting things with a wrench that by the end of the game, I could brain any unsuspecting enemy with a single swipe.