Bjo Trimble's Star Trek Concordance continues to be an essential reference for Trek fans. When she started creating it (from Dorothy Jones Heydt's prodigious collection of notes), Trek fans couldn't Google who wrote an episode or what that random Ensign's name was again in that bridge scene. Trimble took Heydt's notes, scripts provided by Gene Roddenberry, and the final aired versions of episodes to create a kind of encyclopedia, glossary, and episode guide in one, for TOS and TAS.

It wasn't just useful for fanfic writers and researchers, but apparently was also used as a canon reference during the creation of TNG.

Going thorugh it now, after having read many other volumes like These are the Voyages, Captain's Logs and The Fifty-Year Mission, I still found lots of new information, plus got to appreciate the collection of fan art in the front of the edition.

Trimble told my podcast co-hosts and I that she's working on a new edition, and I'm really excited for that.