Inminent Despair
About Single Player... You will get an enourms world to explore, amazing dungeons and enemies, also don't forget the BOSSES. There is way more equipments and items than Demon's Souls... also mana/mp/magic bar was removed... your magic spells, miracles and brand new pyromancy is now casted by charges, each spells has it number of charges, so you don't have mana but your spells may run out when your really need them...by the way it makes the game more versatile, but most of powerful spells has low charges and need too much room in your magic slots.
As the main difference from Demon's Souls this game world is also separated in several areas, but they all are connected each other, instead Warp Swords of Demon's Souls there are Bonfires (Checkpoints) in almost all areas, the purpose of Bonfire is to heal, replentish spells and upgrade/repair equipment.
About Multiplayer...If you played and finished Demon's Souls... you won't have any problems understanding the new and complicated multiplayer mechanics... there are about 10 different items to participate in multiplayer gaming... too much items in my opinion... but when it works... IT REALLY WORKS... also Covenant System (Guilds) was introduced in order to remove World Tendency of previous game...
You get a GREAT time dying and dying... but you'll have fun, that's for sure.
P.D. There is no Meat Cleaver