The Role-Playing Game Books is a term used by Titannica to group together two books, Fighting Fantasy - The Introductory Role-playing Game and The Riddling Reaver, that have proved difficult for publishers and readers alike to categorize into a sub-series. Arguably, the books that are contained in the Advanced Fighting Fantasy system are also role-playing gamebooks, however, they fit within their own sub-series as defined in a number of publications.