Adventures with Crossbow and Rod
Mentioned in Moving Pictures, this is a book about hunting and fishing. Mustrum Ridcully intends it to be a sort of autobiography-thingy, but can never really get the time to sit down and write, how these author johnnies manage to get so much spare time on their hands is a total mystery to me, and so on.
So far he has managed a chapter on the strange and highly specialised species to be found in the River Ankh at Ankh-Morpork, you know, the ones that implode or spontaneously combust on contact with the air (and fresh water).