This is a really fun two player card game that I always wished had caught on more. Its rather complex though, and of course requires at least a modest investment in cards. It's certainly not some sort of re-themed Magic the Gathering though.
The game is for two players only, and takes place in turns. One person plays the evil (or at least greedy) Corporation, who goes first. The Corp, of course, has some sort of secret agenda to take over the world or otherwise improve the bottom line. The other player is the heroic (or foolhardy) Runner. He's a hacker who is out to expose the Corporation, and of course prove how macho he is. It's all very cyberpunk, in other words, with lots of cool artwork and funny pseudo-quotes to give the game nice atmosphere.
The Corp and Runner play the game very differently, which is part of what makes it fun. Basically, everything the Corp has, and is doing, is secret. The runner has to make "runs" on the Corp's various assets to find out what is going on within them, and in particular to find agendas. Agendas are worth points, usually 1 to 4. The first player to get 7 points wins.
The Corp scores agendas by playing them face down onto the table and advancing them. It often takes the Corp several turns to advance an agenda to completion, because playing cards and advancing cards both require actions and money. The Corp generally has plenty of money, but it only gets three actions a turn, plus an automatic card draw. All the runner has to do to score agendas is find them. So the Corp has to do something to protect its agendas while it is working on them (more below). Still, if the Corp scores an agenda it not only gives him points, it usually gives him some sort of nifty special ability, or at least some cash.
That something is mostly "ICE." Defensive software used to protect its agendas from intruders, often with extreme prejudice. Of course the runner, being a hacker, has various kinds of ICE breaking software. But since there are many kinds of ICE, he has to get his hands on the right pieces of software. Once again this requires actions and money. The runner has 4 actions, but he doesn't get an automatic card draw and money is often rather tight. Making runs also costs actions, but may or may not cost money depending on what kind of defenses the Corp has put in his way.
If the Runner can get past all of the ICE then he (usually) scores the agenda immediately. In fact, the Runner can make runs on the Corp's hand (and get to look at one card), draw pile (and see the top card), and discard pile (and see everything). If he ever sees an agenda, *boom* he scores it. Other cards, he might be able to destroy.
The cards that the Runner has in play (not in hand) are almost always face up, visible to the Corp. Everything the Corp has is face down until activated. This means that the Corp has at least some idea what kinds of ICE the Runner is equiped to deal with, as well as what special abilities he may have from hardware and resources, and can lay out his defenses accordingly.
On the other hand, the Runner has no idea what the Corp's cards are until he goes and looks. The Corp has lots of cards that he can play that might look like agendas, even including being advanced, but turn out to be money-making resources or, worse, traps that will hurt the Runner when he accesses them. And then there's that ICE to contend with. It's all face down until activated (for a cost) by the Corp. If the Corp activates some ICE while the Runner is making a run on it, and the Runner isn't equipped to deal with it, then that run is usually ended, and lots of other negative things may happen to the Runner as well.
It is possible for the Runner to get killed. The Corp has cards that, under the right circumstances, let him cause physical damage to the Runner, by, say tracking down where he lives and blowing up his house ("Urban Renewal"). He can also cause "Net" damage to the Runner with feedback through the net, a common effect from ICE. Both kinds of damage force the Runner to discard cards from his hand. If he doesn't have enough cards, he's toast. Then there's brain damage, which not only forces card discards but permanently reduces the maximum number of cards the Runner can hold (normally 5). There are many Runner cards available to prevent or reduce these various types of damage, of course (e.g. "Armored Fridge," or "Expendable Friend").
Whew! With all these rules, you'd think that the game must take forever. Really, though, games rarely last more than 30 minutes. Generally, you play a match, with each player being the Corp and the Runner at least once. Since this is a CCG, there are of course many more different cards out there than you can use at one time, so there's an endless variety of possible decks. There are enough wacky cards out there so that it isn't really possible to build a perfect deck, capable of dealing with anything and everything the other guy might throw at you. Of course, there are some cards that are very powerful (e.g., "The Department of Truth Enhancement," "Newsgroup Filters," "Arasaka Owns You") that can tip the balance heavily in favor of those lucky enough to have them and get them in play.
Generally, play goes something like this. Early in the game, the Corp won't have enough resources to protect his hand, deck, *and* lots of "data forts" with agendas in them. But he can bluff. Bluffing is in fact crucial for the Corp. For instance, he can put down lots of ICE even though he can't actually pay to activate it if the Runner goes after it. He can play an undefended agenda and hope the Runner is afraid to go after it, or better yet play an agenda *and* something nasty, and let the Runner sweat over which one to attack. There are even some agendas that will hurt the Runner as he scores them.
Meanwhile, things are even tighter for the Runner. He'll have no Icebreakers or very few, and little money to run them with. So if he runs on something that is defended he runs the risk of spectacular failure. But if he *doesn't* run on something that turns out to be an agenda, the Corp gets an early lead. Yet running on something undefended could also yield easy points, since the Corp might well have more agendas lying around than he can defend at this point.
This sort of situation generally lasts for the first few turns, but by that time the Corp, with its superior resources, generally has some money stored up and some ICE in front of any obvious targets. The Runner is probably still struggling to get together everything he needs to run effectively, but there are many cards that let the Runner search through his deck for things that he needs, so the Corp's advantage won't last long! This is probably the Corp's best chance to score agendas without interference, but it's always possible that the Runner will surprise the Corp with a sudden influx of cash ("Loan from Chiba") or a new program that lets him evade the Corp's well thought out defenses.
If a game runs long, a decently constructed Runner deck will probably have achieved the advantage. Given enough time the Runner can get enough software, hardware, and special resources to make many successful runs in a turn. Still, the Corp isn't necessarily out of it, since by this time it may have enough special resources of its own to do things like score an expensive agenda in one turn, or use that electromagnetic railgun they built on the moon ("I've Got a Rock") to vaporize the Runner's entire zip code
There are at least a couple of expansion sets to Net Runner out there, which introduce some new variations to play. For instances, one expansion makes it possible for the Runner to give the Corp bad publicity, enough of which forces the Corp to lose. I haven't seen enough of the expansions to say how else they might fundamentally change game play.
All in all, I think Net Runner is an excellent game. In particular, the constant uncertainty of what the Corp is doing/capable of means that every game is unpredictable and stimulating. Plus the cards and the flavor text that go with them are really quite cool. :) If you like CCGs at all, you should like Net Runner.