The Light Fantastic
Even though Pratchett's novels take place in an alternate universe, on a "planet" known as the Discworld, his books are really parodies on the peculiarities of our own world. The Light Fantastic pokes fun at the myths of Armageddon and the religious zeal it engenders in some people. Consequently, entranced, mindless throngs coalesce into book burning frenzies and fanatical lynch mobs.
Through the book, we follow the fortunes of a "failed" wizard named Rincewind who possesses a singular talent for surviving by running away. And run he does, because practically everything frightens Rincewind.
Everything, that is, except the one thing that causes everyone else to panic: The new Red Star that has been showing up on the sky and keeps growing in intensity and heat. As Rincewind's friend Twoflower so aptly puts it: "If there was anything at all to be frightened about, he'd be frightened. But he's not. The star is just about the only thing I've ever seen him not frightened of. If he's not worried, then take if it from me, there's nothing to worry about."
And naturally, Twoflower is correct in his assessment of the fate of the world by way of observing Rincewind, the Discworld's foremost expert on when to panic.
Rincewind and Twoflower's adventurous journey includes saving an unappreciative sacrificial virgin, visiting a forest of talking trees and a lair of friendly trolls, flying through the sky on a rock levitated by druid magic and through the universe in a magic gift store, and narrowly escaping the scythe of Death in the netherworlds: Things that are the stuff of myths and legends in our reality but almost commonplace on the Discworld.
In the end, it's really all about a powerful magic spell that has lodged itself in Rincewind's brain, waiting for the Red Star to appear before reuniting with seven other spells to be read at the appointed time in order to turn the path of Great A'Tuin away from his (or her) collision course with the Red Star.
Great A'Tuin, of course, is the great sea turtle swimming through the cosmos with four elephants on its back, who in turn hold up the Discworld. Just as a clarification for those of you who still cling to the belief that all worlds in the Universe are spherical and revolve around stars by way of gravity.
The Light Fantastic is a great read and highly recommended, though I must caution, it requires great discipline in order to not laugh out loud if read in quiet public spaces such as libraries. It can be read as a standalone book or as part of the series.