
Image from http://www.amazon.com
By fictional non-fiction I mean guide books that explain things about things that don't (or might not) exist. For example, J.K. Rowling wrote several, such as
Quiddich Through the Ages and
Magical Beasts and Where to Find Them. Then Star Trek has many books showing the technical specs of ships in great detail, and charting the galaxy with planets such as Vulcan, Kronos, and Andoria. Have you ever read books like these? Do you consider them fiction or non fiction?