This game will cause you a deja vu.
From the very beginning the game throws you into the shoes of lord protector Corvo in service of a dark steampunkish empire. The events develop rapidly and you will soon find yourself framed and in the middle of political conspiracy, and the only way to redeem yourself and save the day would be to become an assassin with paranormal abilities.
While this all sounds refreshing and intriguing, in reality it can't be farther from that.
First of all the game design is very cartoonish. It's not a bad thing in itself, but it causes a major deja vu because we have seen that before. Dark retro environments? Bioshock check. Cartoonish dystopic posters and weapons? Fallout check. First-person sword swinging and magic? Elder Scrolls check. Air-assassinations? Assassin's Creed check. And that sadly takes away from game's originality because Dishonored stops feeling like a stand-alone title instead appearing like one of these games, just with more whale oil.
Graphics leave much to be desired. The main menu already made me suspicious but actual gameplay only proved me right. I mean it's 2012 now, it's shameful to offer such low-res textures and unreal engine. Another flaw with such design is that it contradicts with dark and mysterious atmosphere game is striving for. It's enough to glance at the character and you can already tell who's a bad guy, so the plot twists become less impressive.
Sound is okay. The voicing seems well-executed and voices do fit the characters. Not much could be said about the soundtrack though. Had it been a little more prominent, like in a similar stealth/action title Deus Ex: HR, the game would be much more engrossing.
The gameplay. I guess it very similar to another Bethesda title, Elder Scrolls. You utilize sword and magic and some long range weapons in the same fashion as you did in Oblivion or Skyrim. The fights are relatively easy though potentially they grow repetitive with same block-counter dynamic. The manner of gaming entirely depends on your preference and again strongly reminds of Deus Ex. You can choose a violent approach with lots of rats and corpses, or you can shed no blood. Again, comparing it to Deus Ex, its mechanics for non-lethal approach were much better and clearer.
The plot. Like I mentioned in the beginning, it's fairly linear and predictable. I doubt that you won't see any plot twists incoming, because cartoonish design is very telling in that regard. Apart from main missions, you can carry out smaller side quests, finding shrines and magic runes among everything else.
In the end, Dishonored is a fairly good game. Hardly deserves the hype and ratings it got, but still it's very tolerable in most aspects. Still if you want a dark game with stealth mode and engrossing atmosphere, I would rather recommend you trying out Deus Ex: Human Revolution.