Set in the "future" of 2010 (Yep, that old) you play as an Uplink Agent. It starts with you "connecting" to the Uplink Servers to create your new hacker identity. After a fake-but-believable-ish "boot up" you are directly connected to your remote proxy gateway, and ready for some plausibly deniable crime. This isn't real hacking, but the way the game presents itself you don't need too much imagination or suspend too much disbelief to leave an exciting doubt in the back of your mind. Easily the most immersive game I have ever experienced.
The game is completely open-ended and very complex, but approachable (There is even an in-game IRC that connects you to a real-life Uplink chatroom to talk to others in the game, if someone happens to be on it at the time.). It gives you an optional, basic tutorial risk-free on one of the Uplink Corporation's testing servers, and there are further tutorials on Uplink's main server, but after that you are left to your own ingenuity. That's a common, repeating theme of this game. Experiment, have some fun. You hacked into the social security database for your last job, what about doing it again to mark yourself as "deceased" to really become a ghost, or hack the criminal records database and put a warrant for arrest out on a server admin that made things difficult for you. In fact, the only way to "beat" this game, is to "break" it. You won't find any "questlines" or the like until you are experienced enough think a bit outside your usual targets...
One of the few games that makes missions non-linear, simply because these aren't missions, they are contracts. A deal between you and an anonymous individual working on behalf of a random company. You can go ahead and tell your employer "Nope, not in the mood, have someone else do it." after you accept the contract... for half the pay up front! (Although, good luck getting another job if your reputation is too spotty!) Perhaps someone paid you to give the guy an A, and on a whim (and after your paycheck), you put his "D-" right back. What about this investigation of corporate corruption? You have it all tied up, got your pay and everyone is happy. But you still have access to the thief's account, and for a short window of time, it's still filled to the brim with your employer's siphoned money.
Backstab at your leisure(and peril), none of it's scripted.
On the negative side, if you look at the screenshots, that's pretty much how the game looks. You can install themes to change up the color scheme if the sharp black+blue hurts your eyes, or you just want to tell people who come over that you are hacking the matrix. Throughout the game there are very few graphic representations, and when there are the best you could hope for is an animated picture (usually just static images, though). It would be easy to dismiss these issues as "part of the experience" but that's just a cheesy way of dodging "Its a really old game, you will have to deal with terrible graphics". Admittedly, though, it IS easy to overlook the visuals, simply because its what you expect to see on some TV hacker's monitor.
Gameplay-wise, once you know how to do it, and get personaly experinced with it, you can get all the money you ever want within a few hours from starting and there is little replay value until you leave long enough to forget how to play. This is problematic and game lenght ties in directly to how good you are at it. You could beat the game in an hour and a half if you know what you are doing.
Don't spoil it for yourself and look up how to start the ending! You will have more fun figuring it out for yourself!
Being a very old game, it also has interface problems. No scroll-wheel support being the worst offender, the necessity to have your mouse hovering over any information box you are trying to type in is a close second. Its a pain, and something to be aware of, but it doesn't get in the way of enjoying the game once you are used to it (Using the tab button is an easy fix to the second one).
At the end of the day, Its certainly worth the 10$, but should you still be on the fence about it, it goes on sale for crazy low prices. Just whatever you do: make SURE you don't miss out on this game!