The Colour Of The Magic by Terry Pratchett (Bg subs) torrent

The main character is an incompetent and cynical wizard named Rincewind. He involuntarily becomes a guide to the naive tourist, Twoflower. Forced to flee the city of Ankh-Morpork to escape a terrible fire, they begin on a journey across the Disc. Unknown to them, their journey is controlled by the Gods playing a board game.

They visit Wyrmberg, an upside-down mountain which is home to dragons that only exist in the imagination. They nearly go over the waterfall on the edge of the Disc, only to be rescued and taken to the country of Krull, a city perched on the very edge of the Discworld. The Krullians wish to discover the gender of Great A'Tuin, the giant turtle which carries the Discworld through space, so they have built a space capsule to launch over the edge. They intend on sacrificing Rincewind and Twoflower to get Fate to smile on the voyage. Instead, Rincewind and Twoflower hijack the capsule in an attempt to escape and are launched off the Disc themselves.

The story is continued in the succeeding Discworld novel, The Light Fantastic.