"
The Encyclopedia of Science Fiction" (St. Martin's Press) is probably the most
comprehensive reference work on
science fiction literature, concepts and authors. Its editors are
John Clute and
Peter Nicholls. The first edition was published in 1978 and won a
Hugo award as the best nonfiction
SF book of that year. Since then the work has been constantly updated and revised, culminating in an even more comprehensive second edition in 1993.
Since 1997 there is a companion volume on
fantasy, aptly titled "
The Encyclopedia of Fantasy" (ed.
John Clute/
John Grant), as well as an "Illustrated Encyclopedia of Science Fiction (ed.
John Clute).