Why is Demon's Souls seen as being a 'hard' game?

[Dahum]

for me i LOVE exclusive games to the PS3 & i always find them very enjoyable,thats why i bought Demon's souls & also i thought the gameplay was kinda cool & it was my first RPG game & my last!.........it was the first game i bought NEW & sold it a couple of days later coz i was dying like CRAZY which made me so frustrated & i never liked the RPG elements

so safe to say it was VERY HARD for me.