The Light Fantastic (Discworld Novel 2)

'What shall we do?' said Twoflower. 'Panic?' said Rincewind hopefully. He always held that panic was the best means of survival. As it moves towards a seemingly inevitable collision with a malevolent red star, the Discworld could do with a hero. What it doesn’t need is a singularly inept and cowardly wizard, still recovering from the trauma of falling off the edge of the world, or a well-meaning tourist and his luggage which has a mind (and legs) of its own. Which is a shame because that's all there is...