great game and........
the farther you dig in deep on dark souls the darker it gets the more the demon's get stronger more hedious and fearsome. it's like playing a game on your toes which is considered great.
the open world structure of the game is the biggest change thart occured in dark souls since it's predessessor.Having this time around bonefires as resting places as contrary in what demon's souls had the nexus and single mission on every world here it's just a big world for you to explore....so there is a little addvantage than demon's souls is that this time around you can use these bonfire as checkpoints but get your hopes up they are really really far away
As for the online not much is changed. you still see ghosts of other players moving around in the game and you can still summon players to help you clear an area or defeat a boss. pvp is still present in the game as it was in demon's souls
death in dark souls is punishing just as demon's souls you lose any collected soul and humanity after death you can still manage to collect your lost souls by touching your own bloodstains but if you dei before you lose them for good
the gameplay is most satisfying in dark souls being an action RPG it is very smooth as it was in demon's souls
finally Dark souls is not a game for you if you just to play it for fun it's a game that is beaten by blood sweat and tears but rewards more than you could ever imagine
good luck in it you'll gonna need it