I just played an hour into Black Plague, and for the most part I was pleasantly surprised.
There's a tutorial at the beginning that's helpful, and a quick recap of the story in Penumbra: Overture. You can also pick a difficulty setting (there are three levels), with "Easy" specifically for people like me who don't like action/tricky stealth sequences. This setting doesn't eliminate these sequences, but does make them, well, easier.
* * * * * * * * * * * * * * * * * * * *
The physics-based gameplay is unusually creative -- I can see now how this can be adapted to give some unorthodox ways of approaching puzzle situations. It's fun to be able to pick things up and toss them around the room (your player character apparently does some weight-lifting in his spare time

). And I enjoyed being able to change the environment -- move things around and leave them where I want them, stack things on top of other things, swing things hanging from a hook, etc.
That said, there is some frustration in dealing with objects -- trying to get a chair to stand up normally was surprisingly difficult, and carrying long planks in these tight quarters requires some trial and error to keep from bumping into walls and other objects. This is not a game for the impatient gamer.
Movement is easy if you're used to panning with the mouse and moving forward with the "W" key. It's first person perspective.
Environments so far are a prison cell, a refrigerated room, a storage room and quite a bit of ventilation duct. It's spooky, with an atmosphere that, while not nerve-wracking yet, does heighten the senses and make you anticipate fearful things lurking around the next corner. I haven't met any monsters, but I've heard one.
* * * * * * * * * * * * * * * * * * * *
One downside -- twice in an hour the screen froze for about a minute, then gameplay resumed. There's an auto-save system, as well as extra saves that are based on reaching special "rewards" -- this means that if you quit between available saves, you will have to repeat everything when you return to the game.
You also die frequently, though you don't lose your inventory when you are respawned or revivified or reanimated or whatever.

* * * * * * * * * * * * * * * * * * * *
I'd say that this game would be good for gamers who want to try something different than the traditional adventure, have the patience to try something new, and enjoy an atmosphere of horror. One hour in, I'd say that so far it fits the definition of an adventure game.