The idea of the first _Deus Ex_ game was that you played this nanotechnologially-enhanced secret agent who worked for the UN's security forces to fight terrorists. But as the game progressed, you learned that the people you were supposed to fight weren't the villains of the story, and that the people you were working for were more than a little evil. After some considerable hugger-mugger about Area 51, the Illuminati, the nature of governments and power, you arrived at a choice of three possible endings, with the world profoundly transformed in three different ways. The mise an scene was actually fairly sophisticated: one might pick up a book on a shelf, and find that it contained an excerpt from _The Man who was Thursday_, and the characters you encountered might offer some philosophical insight out of de Toqueville or Machiavelli or Thomas Paine.
The other virtue of the game was that it gave the player a degree of choice. Tasks weren't that simple, and the game offered several ways of accomplishing them. If you wanted to run in with guns blazing, you could do it... but you could also use stealth and cunning, avoid killing people, and generally add to your suspense.
This sequel's set a few years after the first, and they've upped the play-as-you-like aspects. It's possible to play through the game without killing anyone. As you play, you're given missions from various factions that frequently contradict one another: the secret agents of the Tarsus Academy may want you to rescue a scientist and protect his new weapon, but a religious faction called The Order may want you to assassinate the guy and take his weapon for their use. Your decision will affect later events; those factions may help or hinder you later on. (Sadly, the game does arrive at a point with three choices, so all of this coalition-building goes for naught. It's fun while it lasts, however.)
The game also provides a certain dry wit. A continuing plot thread involves a war between two coffeehouse chains, Pequod's and Quequeg's, and you're occasionally asked to do favors for one side or another (burn the competition down, talk a pop star into endorsing one brand or another, etc.). There's a pop star, NG Resonance, whose holographic presence in various nightclubs establishes her as one of your best friends... but a meeting with the real NG is a funny surprise. (The game passes up a chance to include a sinister edge to this virtual-Britney.) About halfway through, one learns a perhaps-not-surprising truth about several of the factions involved. One has the feeling that the game-makers could do a wonderful black comedy with the same premises and game engine, along the lines of _The Manchurian Candidate_. (I wish Warren Spector'd hire me as a writer.)
About a month ago, they released a demo of the game, which was a severe disappointment. Between the limited play and the X-box interface, a lot of gamers were extremely angry. But once you get used to the changes from the previous game, this one is extremely good, and every bit as much fun as the first _Deus Ex_. And how many games allow you to end it all with the words of Michel Foucault?