Going over the edge

I read a series of books in the mid 90's written by Terry Pratchett. They were science fiction/fantasy and I loved every single one of them. His description of how the world in the physical sense ends always helped paint a vivid picture for me of the world his characters were living in. The planet was called Discworld, and it was a flat disc on top of a giant turtle, floating through the galaxy. Water just flowed off the edge of the world, endlessly.
Sometimes I wish the world were flat so I could just walk in a straight line all the way across it, double back, and then walk over the edge, down the waterfall, just to see what lies beyond it.
Or maybe it could be like the world of The Little Prince, a round world that he walked around and around. I haven't read that book or been read that book in so long that I can't remember much more than the cover-a little boy in a blue shirt, broom in hand, defying gravity.

Part Two