I played it, but I sucked too much so I printed off a 400 page guide, and got bored of reading.
You are the worst kind of person, seriously... xD
Demon's Souls is just intensely difficult, the story is very dark fantasy, almost like Dragon Age, but there are no other people other than a handful of characters in the Nexus (the hub).
There are five world, that most people identify like Mario stages, 1-1, 1-2, etc.
The stages are a decent size and the game saves quite often so you can quit whenever and end up right where you quit.
When you die, instead of it being game over, you are resurrected at the start of the level as you soul, where your HP is cut in half, but you do more damage. The fun part is PVP and Co-Op (Black Phantom and Blue Phantom respectively) where someone can enter your game (When you are alive) as a Black Phantom, and try to kill you, so they can become resurrected. The other option is to become a Blue Phantom, and enter someone else's world to help them defeat their Demon, which will result in the Blue Phantom becoming resurrected and returning to their own game.