The Light Fantastic

The story picks up exactly where The Color of Magic left off, with Rincewind and Twoflower falling off the edge of the world. They are rescued, in a fashion, because the most powerful spell in the world, one of the eight spells of the ancient book called the Octavo, has been hiding in Rincewind's brain for years and does not want him to die. Meanwhile, astronomers notice that a red star is getting bigger, and the wizards of Unseen University realize the world may be in trouble.

Rincewind and Twoflower wander through enchanted forests, a gingerbread cottage, an ancient stone circle and a frozen wasteland, followed everywhere by the Luggage, a chest made of magical wood that walks on hundreds of little legs and eats anyone who threatens its owner. They meet Cohen the Barbarian, a legendary hero now in his eighties, and Bethan, a young woman rescued from becoming a sacrifice. Back in Ankh-Morpork, the ambitious wizard Trymon schemes to take control of the University and the Octavo. Death, who speaks in capital letters, makes several memorable appearances.

Fast, silly and surprisingly kind. About 288 pages in paperback, and the second of more than forty Discworld novels.