I didn't think the trailer looked all that great, but I'll give the demo a shot. Is it out now?
If you like games like Bioshock, Dishonored... stuff like that... you should like this. I know I'm going to.
Demo starts out in the "build up" set up beginning of the game so yes, it's kind of slow at first and then the intrigue and shenanigans start kicking in. Be patient with it.
Tip: Sound matters. You can hear these mimic enemies if they're hiding if you move slow and quiet and listen for it. I highly recommend going in the menu and turning the game music WAY down to like 10 or 20 because it isn't that good IMO and can interfere with the above.