It's probably old news but I don't think it's been mentioned here before but anyway if any of folks are interested in the lore and development of Darks Souls then there's a (Japanese language only) book called Dark Souls Design Works. It's mostly filled with concept art but more importantly it explains why the things the way they are as well as some bits of trivia and lore. I'll post a video review I just stumbled on recently where the guy talks a little about what he read (but not giving out too much in respect to the developers.) Some interesting key points include the Black Phantoms that were invading people who broke the street date, why Gwynevere breasts were so unusually large(!) and why Logan was the way he was when you found him on the top of the Duke's Archives.
As I said before, it's mostly concept art but every little tit bit of information when it comes to this game is rather worthwhile. Anyway, I just thought some of guys might be interested.