The Color of Magic (Discworld, #1)

by Terry Pratchett

It was all very well going on about pure logic and how the universe was ruled by logic and the harmony of numbers, but the plain fact of the matter was that the Disc was manifestly traversing space on the back of a giant turtle and the gods had a habit of going around to atheists’ houses and smashing their windows.

All Rincewind could manage to say was, “You know, I never imagined there were he-dryads. Not even in an oak tree.” One of the giants grinned at him. Druellae snorted. “Stupid! Where do you think acorns come from?”