An A-Z encyclopedia covering subjects from Andorians to Zefram Cochrane to Atoz, the Star Trek Encyclopedia was compiled by Star Trek: The Next Generation, Deep Space Nine and Voyager staffers Denise and Michael Okuda. It includes summaries of all episodes, descriptions of all characters, rundowns of all locations, data on all lifeforms, and details on all starships that appeared in the Star Trek universe up to the fifth season of Voyager, and the final season of DS9 in the third edition.
Not taken into account are officially non-canon works - such as the various Star Trek novels, games - and The Animated Series.
Some articles (generally only a paragraph or two long) contain little known facts from behind-the-scenes, presented in italicized fonts. Many also featured images created specifically for the Encyclopedia, including shots of barely visible starships like the Saber- and Akira-class vessels, and a photograph of Cochrane's statue.
The only "official" exhaustive reference work that is still updated is the Library of StarTrek.com, though this sometimes contains discrepancies.