Great game. If you enjoyed Human Revolution, you will definitely enjoy this. It gave me a solid dose of playing stealth games that I need so it will be a while till I get onto Dishonored 2. Highly recommend.
Edit: I thought you guys might want some more info. All up my first (and only) run took 30-35 hours, around the same length as the first DE:HR. This is including all side missions and exploring pretty much everything. I spent quite a lot of time exploring, it's pretty fun and the side missions are few and all worth doing as some have an impact on the games outcome.