93 Million Miles in a Balloon is an old novel that is no longer in publication. It features the fictional explorations of a hot air balloon explorer, Dr. Gustavius Boles, and his stowaway, Lord Caleb Trimingham. Arthur received a copy of the book from Mr. Fox, who read it a long time ago. Due to the book being out of print, used copies are difficult to find - the only used copy Arthur could find costs $1,000. The book was adapted into a musical, but the musical bears little resemblance to the book.