This book was written using 100% recycled words.

The line is a playful, self-referential joke about originality and authorship. By claiming the book is made from “100% recycled words,” it points out the obvious-but-easy-to-forget fact that all writing is assembled from a shared, finite vocabulary; what matters is the arrangement, voice, and ideas rather than inventing new “raw materials.” It also parodies environmental marketing language (“100% recycled”), turning it into a literary quip that fits Pratchett’s broader comic style: puncturing pretension while celebrating craft. The humor works because it is simultaneously true (words are reused) and absurd (no book could be otherwise).