I loved Terry Pratchett's books and had tried to play discworld a few years ago, but at that time I was intimidated by the complexity of the world. But (obviously) I tried again some time last year, and I just love it! Even if you haven't read the books, the world is full of quests and challenges that you wouldn't find on most muds. They are all original, and the room descriptions actually change according to the time of the year! (You have to pay close attention to room descriptions, because sometimes they contain clues to quests)

The mud has several different channels, and in general, the crowd tends to be semi-decently educated. (By that I mean that swearing is not tolerated, and the playerbase tries to act intellectual ;) [O.k. I'm kidding. Anyway, I mean swearing is not allowed on public channels and there can be some fun pseudo-intellectual conversations occasionally].

Pk is optional, and since one gets exp for existing on the mud, you can choose how you wish to play. You can either go off on mad killing sprees, sit idle and chat, or work on spells, potions or quests. In other words, something for everyone! :)