The Discworld is very much like our own - if our own were to consist of a flat planet balanced on the back of four elephants which stand on the back of a giant turtle, that is . . 
 
'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 . . .