The story is rather standard, nothing refreshing or particularly exciting. The main character has a mysterious past, they are being lied to, there's plenty of conspiracies. There is a bunch of stereotype bad guys, who you get to kill off one by one through the game in boss fights, but also a couple of "grey zone" characters that you aren't quite sure of on who's side they are. The appearance and personality main character Adam Jensen is a plus, there are very few main characters out there who are more bada**.
The game lore is more or less taken from the old 80s Robocop movies, the game seems heavily influenced by those, to the point where there are in-game jokes about the similarities: ex-cop, nearly died, implants saved his life, he gets superhuman powers, wants to get revenge on those who messed him up, story takes place in Detroit, there are similar huge guard robots like the ones Robocop was fighting etc etc.
I have the feeling this game received a whole lot more hype than what is justified. A lot of the hype both by the developers and reviewers seems to revolve around the game having some unique moral considerations for the character/player. If you bought that moral debate hype, you will be disappointed. The moral dilemma of the game is whether humans should allow implants to give them supernatural features or not, become 'augmented'. Even though this has a faint, far-fetched connection to today's debate of DNA research, the whole moral debate just seems alien to me, it doesn't interest me. Because whether humans should become cyborgs or not is simply not a real moral dilemma I had to ever consider in the real world.
More interesting is that you can often decide whether to be merciful to your foes or kill them. You can sneak past them, knock them unconscious or kill them. Neither has any major benefits, save for a tiny xp bonus after the mission if you managed to go through it completely unnoticed. The former is the hardest by far, and gives most of a challenge.
However, if you decide to be the stealthy type who just slips past everything, you will suddenly find yourself finding a monotonous puzzle game rather than a first person shooter. Every level you play is very much the same, you sneak about either in some office complex or industry building most of the game.
Alternatively you can just shoot your way through. This is easy early on in the game, but gets harder when the foes get tougher. The controls are rather crappy if you are used to playing games like Call of Duty. Redefining the controls is a -must-, set iron sights (ie scope) to right mouse button, and set take cover on some other button, it is rmb by default. For an augmented superhuman, the character is also rather sluggish, even after maximum leg enhancements. So fire fights is mainly about taking cover and waiting out your enemies, then shoot them as they get close. The selection of weapons is rather boring, and as in most games you can get mods for them to upgrade them in various ways.
You can also chose a middle-ground between stealth and frontal assault, which is the easiest way of playing. There is a fun close-combat option that allows you to either knock out a foe that's up close, or kill them. I believe the former makes a bit less noise, but if you leave unconscious foes around, other enemies can find them and wake them up. For some quests you need the bad guys alive.
With the sneak element, the choice to knock out enemies silently or loudly shoot them, the option to hide away the bodies... this game is very very similar to the Hitman - Codename 47 series. If you liked those, you will like this game.
The graphics are good, in terms of combat and movement. The environment is poor however, you spend the whole game either in 1) dull office environments, or 2) dull industrial complexes (with lots of wooden boxes), or 3) dark, gloomy alleys. Weather, lighting and other such environment effects are minimal.
The game runs smooth and without any technical problems or notable bugs.
Overall, this is a very linear game. Don't believe anyone who tells you there is a lot of alternatives or sandbox elements: there is not. There is a linear story with a few side quests, and the game has no replay value. As a veteran gamer I beat this game in 3 days of casual playing, on the default difficulty level, doing every side quest. You do change the storyline a tiny bit depending on your choices, but overall the game is as linear as the average EA mainstream one.