Well, this is just plain fantastic on every level...
Deus Ex is one of the only games that I can think of that offers such a tremendous amount of interactivity with your environment and total freedom of action. You can thoughtlessly blow away anyone without consequence... though it may not be a very good strategy. The plot is extremely reminiscent of an X-Files episode.... a really GOOD X-Files episode. You will deal with the Illuminati, the unknown powers of FEMA, vague hints at the existence and origins of the "gray" aliens... even direct encounters with the mysterious "Men and Women in Black". Hell, you even get to pay a visit to a post-nuclear strike Area 51.
If that doesn't temp you to buy this game perhaps this will. Deus Ex combines many of the best features of an RPG and an FPS. Yes, you walk around FPS style, able to draw a gun at any moment and start shooting. In fact, there isn't any restriction to where, when, or why you can pull out a weapon and start shooting anyone and anything you like. But, like a good (and rare) RPG, there are real consequences to all of your actions. Did you waste that guy in the subway for no reason? Well, you may not find out from him where your enemy is hiding out at. Did you mercilessly murder the electrical repairman aboard that ship? Well, it may be a lot harder to accomplish what you are attempting without his help. The point is that your decisions, though yours completely, will have a definite impact on the difficulty of the game. Yes, you can try to blaze through the game shooting everyone in sight, but you may have more success sneaking around and using discretion here and there.
Additionally, the fact that you can upgrade the abilities of your character is a welcome change, even for the finest FPS games such as 'Half-Life'. There are a limited numbers of "Upgrade Canisters" that you will have to use throughout the game. These will determine what special nanotech abilities you will be able to use, such as bullet-proof skin, or the ability to see though walls. You also must determine what weapon and non-weapon skills your character will possess. Do you want a lock-picking sniper, or a computer hacker able to jump off 20-story buildings without a scratch? A combination of the two? Something else entirely? It's totally up to you.
Everyone who owns a computer capable of running it should own this game. Whether you enjoy a hardcore Doom-style FPS, or a classic Pool of Radiance (Gold Box series, not that 'Ruins of Myth who-knows-what' mess) style RPG, this box should grace your shelf. If there is a brain in your head, you will enjoy this game. If that brain is a "thinking mans brain", you will adore this game.
Furthermore, replay value is amazing, as you can discover major new plot twists (though not affecting the overall outcome) by doing a few key things differently (does Paul really have to die?).
All other realism aside, the AI leaves something to be desired. The problems aren't everywhere, but too frequent for a game of this quality. There are times you can pick off enemies with the sniper rifle, and nobody really notices. Other times you can slice someone to death with the oh-so-quiet Dragon Sword and the whole world seems to have found out about it... alarms abound. The ending sequences could have been a bit more long and detailed, but that didn't stop me at all from playing the game fully three times through, and being amazed each time. Like a good mystery novel, each "read" allows you to realize nuances of the plot you may not have caught before.
The Bottom Line
In general, there is absolutely no reason not to purchase Deus Ex. I am almost certain that any gamer would enjoy it, regardless of their usual preferred genre of game. An FPS freak will love it, as will the hard-core RPGer. If you are a novice to the first-person shooter, this game is a perfect introduction (though nothing else will live up). Bottom line: BUY THIS GAME! It's sure to be remember as one of the best ever.