Where else but the Discworld would a revolutionary treatise be called "What I did in my Holidays"?
Twoflower the tourist (see The Light Fantastic) has returned to his home in the oppressive Couterweight Continent, and his account of the joys of life in (extremely) free Ankh-Morpork has become a rallying influence for the Red Army.
They summon the services of "the Great Wizzard", aka Rincewind (Twoflower used a lot of artistic licence in his account), and he arrives, transported by High Energy Magic (by other wizards, naturally).
Then there's the Silver Horde, led by Cohen the Barbarian with the assistance of a teacher called Mr Saveloy (in the local language, that's Mr Stuffed Tube). Under Mr Saveloy's guidance, the Horde learn how to have social intercourse ("hur hur hur... sorry") and tone down their language, which makes for some of the funniest dialogue imaginable.
Like every other Pratchett book I've read, it had me laughing the whole way through, taking in the comments with a wry smile, and marvelling at the way it all fitted together. Just great! (Dies ist eine Amazon.de an der Uni-Studentenrezension.)