Dishonored isn't revolutionary, but it is well worth playing just for it's originality alone.
The story is a bit simplified: You are Corvo, bodyguard of the Empress of Dunwall, a city cursed by a nightmarish plague which threatens the entire population. When things appear they can't get any worse for the city, the Empress is murdered by a group of mysterious assassins, and Corvo is set up, appearing to be responsible. While awaiting his execution, he is rescued by a group of people who predict he didn't really kill the Empress.
In order to prove his innocence, and get his revenge, Corvo must find the people responsible for the murder of the Empress. This involves taking on various assassination missions as he uncovers the truth and alternatively, shapes the future of Dunwall.
Dunwall feels like a character itself. With a new exploration of a scientific use of whale oil, the city now has working machinery. Dunwall is in a industrial age, but even this new technology has not been able to cure the plague, a sickness devastating the city. Dunwall isn't the only interesting character though; you meet a variety of different people who help you on your quest. Beyond that, the targets have very interesting stories that you slowly uncover as you attempt to bring them to justice, and one of the cool features which reveals the back-stories of these characters is a talking heart, a item you obtain early in the game. As you aim it at people you can discover their struggles, dreams and mistakes. This heart also gives some back-story to the locations you visit, telling dark secrets of the past.
The game can take 5-20 hours, depending on how you play. If you try to fight your way through it, it's unlikely to last more than 10 hours; but even doing that has it's consequences. Levels will become much more brutalizing, certain story events will unfold differently, and this will lead to a different ending. Playing it as a stealth game will fetch about 10-12 hours of gameplay, depending on if you do any side-quest.
There are still things to do after you complete the game though. The environments are opened for choice, and enemies often appear in different areas of the game. This adds a tremendous amount of replay value, since levels rarely ever play out the same. There are also multiple endings to obtain, as mentioned previously.
Gameplay is easily Dishonored's best aspect. You have to take on various assassination missions, but how you dispose of your targets is your choice. The levels are massive, and there are multiple paths to take in order to reach your goal. Sewers, vents, rooftops and even light poles are all usable, which open up several opportunities. You may decide to use chandlers to venture above, or use an abandoned sewer drain. The choice is yours.
You are armed with a crossbow, sword and gun: But these are not your only tools. Near the beginning of the game you are gifted with the ability to use supernatural powers, including being able to turn into a rat, possess guards, teleport, or even stop time. These powers are one of the best features in Dishonored, since combining the powers never gets old. For example, you can teleport to rooftop, stop time, and rain down a volley of arrows on your targets in a matter of seconds.
These abilities open up the different possibilities even more. If you want to quickly clear a room you can stop time and assassinate everyone nearby. If you prefer a more stealthy way of playing, you can perhaps possess a rat and look for a vent. The levels aren't big enough to be called open-world, but there's certainly enough ways to reach your target that you never feel isolated.
Normally, you would expect the choices to all lead to the same result: The assassination, but this isn't true at all. Miraculously, you can complete the entire game without killing a single person, and instead use other means of dealing with your targets.
The A.I is incredible for the most part. They react precisely to sound and sight, and work together perfectly. The game is punishing, and it's difficult to defend yourself in a head-on fight. Just a few hits can kill you, so taking on multiple enemies is highly challenging. Sometimes the A.I can be less amazing in other situations though, since they don't often find the death of another guard terrifying. Even when a guard disappears from his post they only give one line and then they return to their patrol.
Technically, the graphics aren't very impressive. But, artistically they are outstanding. The world is crafted around this brutal back-story, and it does a great job of bringing it to life. Just looking down a street tells you about the place. A colossal bridge overlooks the broken streets, Rats explore forgotten sewers, and all the locations are brought to life by crisp lighting effects. Just by using the art style, you can tell Dunwall was once a great kingdom, but now it is a broken civilization. Animation isn't as good though. Characters are clunky, and their movements are limited.
The soundtrack is ultimately, impressive. It's a perfect blend of low tune mystical themes and fast-paced fighting music. When it comes to stealth, audio is extremely important, and Dishonored pulls it off quite well. You can hear faint footsteps, and the mumbling of the guards off in the distance. The sounds of machinery echo throughout the city, and all the combat sound effects are spot on. The voice-acting of the various characters is also outstanding, and the writing is noteworthy. However, the guards have limited lines, and often you will hear the same phrase repeated multiple times in a mission. It's a small issue, and it isn't exactly annoying, but it definitely stands out.
The one minor issue I have with Dishonored is it doesn't have New Game+, a feature which can add enormous replay value. Although it appears the developers want you to experiment the various ways you can tackle missions, it would be much more effective if you could use your upgrades only obtainable later in the game on earlier missions.
Dishonored is a game of many words. The lack of New Game+ is a bit distracting, but if you look beyond that very minor problem, you have a decent story, addictive gameplay and the most atmospheric world since Bioshock. The combat feels tight, the stealth feels solid, and you are sure to have plenty of fun no matter how you decide to play: Both ways are equally as amusing and exciting.
Dishonored mainly stands out because of it's originality, it's freshness. Although it isn't innovative, Dishonored crafts it's own identity and this along makes it a game worth playing. It isn't exactly revolutionary, but nonetheless Dishonored is a spectacular adventure unlike any other.