Spin Offery

Catch-all term for books written about something popular in another medium. Star Trek, Star Wars, Doctor Who are the common culprits, but by no means the only ones. Of varying quality, often can be the Mills And Boon of the SF world, very formulaic writing with nothing very interesting to say, but sometimes a place a good author can be found. For example, Diane Duane, writer of the So You Want To Be A Wizard? trilogy, is better known as an author of Star Trek spinoffs.