From the introduction:
The purpose of the Fancyclopedia, not fully realized, is to define all expressions, except nonce-words, which have an esoteric meaning in fantasy fandom, and to supply other information, such as that on Esperanto, which may be needed to understand what fans say, write, and do. It should be remarked, however, that fans make many allusions to materials in prozines, fanzines, and other places, which no reference work could cover completely. Certain fields have been excluded from the scope of the Fancyclopedia because they are well taken care of elsewhere. While nicknames of fans and pet names of fan magazines are identified here, biographies have been left to the various Who's Whos of fandom, and fanzines in detail to Dr. Swisher's excellent S-F Check-list.
User summary:
Fancyclopedia was published decades before the first roleplaying game products, but is nevertheless a curious and significant artifact in the gradual development of science-fantasy fandom, which in turn heavily influenced the first decades of roleplaying.