Marjorie Daw is a librarian, and takes her job - and indeed the truth of words - very seriously. She doesn't know it, but her world and ours - Roundworld - is in big trouble. On Discworld, a colossal row is brewing. The Wizards of Unseen University feel responsible for Roundworld (as one would for a pet gerbil).
The 4th book in the "Science Of Discworld" series, in which Pratchett provides a new story set in his fantasy world, and Ian Stewart and Jack Cohen examine the science and philosophy which it explores. This time the trio take on The Really Big Questions: God, the Universe and Everything Else.
