Just like Dona, I'm also fairly new to Deus Ex, many friends recommended the first game over the years, and I know it's like the sacred cow of PC gaming, but never made it past the first level. Out of curiosity I tried the demo of the second game when it came out, but didn't really like it, and now I'm playing Human Revolution, since it's a prequel anyway. It's not perfect and not nearly as beautiful as TW2, but it's so addictive!
It's like Blade Runner taking place in near-future Detroit and you play as Adam Jensen, head of security at Sarif Industries, the most powerful corporate in the city. In the tutorial you're immediately thrown into the middle of a powerful attack against the HQ. Jensen is among the very few survivors, but in order to save his life, his body gets heavily augmented and he ends up being more robot than human. As you progress through the game and follow the leads on the attack doing quests, you gain XP and can unlock your dormant new superhuman abilities.
Since I love stealth games such as Thief, MGS or Splinter Cell, I really enjoy sneaking around, breaking into apartments, robbing people blind, and hitting them from behind. I spent most praxis points on hacking skills so far and probably the majority of people do the same because stealth style gameplay is the most rewarding. Just gimme a stun gun and I'm good to go, if I wanted a simple cover shooter, I'd play Gears of War.
I managed to knock out everyone during the first mission and got the ghost bonus, it was worth all the quick loads.
I like how the game switches to TPS view whenever you take cover, climb a ladder or take out enemies (the takedown animations are so badass), I also enjoy the hacking minigame and the conversation system, but exploring this yellow-grey steampunk world full of secrets, easter eggs and occasional pop-cultural references is the best. The story is good and important characters are quite entertaining, my favorite is Pritchard, the prick IT guy with the cool voice, and Ezekiel, the one-eyed terrorist bro who ripped the augs out of his body. Damn.
Prepare for Bible references and don't forget that Adam means human. SO DEEP.