You can get the Dying Earth RPG on Drivethru. The update to the rules is the Revivification Folio. You can also get the book in the traditional format. And you should read the original stories
Somehow I failed to mention that a) of course, the Dying Earth stories are where the D&D magic system comes from, more or less, and b) that one of my favourite things about Paranoia is that its definitive artist and I have the same name. He even once sent me an email headed "evil clone must die!"