The Color of Magic by Terry Pratchett

“Tourist, Rincewind had decided, meant ‘idiot’.”

Twoflower is the Discworld’s first tourist. What that means exactly, nobody knows. What it means for the wizard Rincewind is that he is probably going to die. From the Broken Drum Tavern, the future site of one of the worst fires in Ankh-Morpork’s history Rincewind and Twoflower embark on a harrowing and hilarious journey that will take them through some of the Discworld’s most picturesque and dangerous sights. Come see the Temple of Belshamharoth the Eater of Souls and Sender of Eight; the Wyrmberg, an upsidedown mountain inhabited by dragons that only exist in the imagination, but that can still kill you; and the majestic city of Krull, where you’re just in time for the human sacrifice.

It’s the kind of vacation that drive Rincewind and Twoflower over the edge, the edge of the world.