I assumed I'd find this info in here and couldn't, so I'm taking a shot at it. Here's a list of all the writers I'm aware of that wrote for Star Trek in movies or television, but also wrote novels or other Trek media. I assume I don't have every single instance, so would welcome additions or corrections: Gene Roddenberry, Film novelization D.C. Fontana (wrote on TOS, TAS, TNG, DS9, produced TAS and TNG) a Pike novel, co-wrote several comics and video games, fan film Roberto Orci, (produced and wrote the Kelvin timeline films) plotted comics series Alex Kurtzman, (produced and wrote the Kelvin timeline films, producer for Discovery and Picard) plotted comics series Brannon Braga (produced and wrote for TNG, VOY, ENT, also wrote 2 films) co-wrote Hive mini-series Jeri Taylor, (producer and scriptor for many TNG and VOY episodes) Several VOY novels Kirsten Beyer – (wrote episodes of Discovery and Picard, producer on Picard) Novels, short story, plotted several comics series Judith & Garfield Reeves-Steven, (writers and co-producers on ENT) Novels, short stories, comics, video game plot David Goodman, (writer and consulting producer on Enterprise) TOS Novels, in-universe reference book Melinda Snodgrass, (writer, story editor and script consultant for TNG) TOS novel [LEFT][SIZE=4][FONT=Open Sans][COLOR=rgb(20, 20, 20)] [/COLOR][/FONT] [COLOR=rgb(20, 20, 20)]David Mack, (co-wrote DS9 episode, consultant on upcoming series) Novels, short stories, ebooks, comic mini-series, video game[/COLOR][/SIZE][/LEFT] David Weddle, (wrote several DS9 episodes) Plotted a novel Mike Sussman, (wrote episodes of VOY and ENT) Plotted an ENT novella David Gerrold, (writer on TOS and TAS) TOS Novel, novelization, comics, fan films John Ordover, (co-wrote a DS-9 episode) SNW short story, ebooks, co-wrote comic series David Bischof, (wrote two TNG episodes) TNG novel Diane Duane, (wrote a TNG episode) Novels, short stories, comics Terry Matales – (plotted two VOY episodes, produced a Picard episode) co-wrote comic series David George – (Story credit on Voyager) Novels, short stories, Alan Dean Foster – (plot for ST Motion Picture) Numerous novelizations, a TOS novel
You'll want to add Denny Martin Flynn, co-writer of ST VI. He wrote the Trek novel The Fearful Summons.
I think this also needs to include Michael Jan Friedman, who co-wrote at least one episode of Star Trek Voyager, as well as being the second-most-prolific author of Star Trek novels in the history of the franchise. Also deserving of inclusion is James Swallow, who co-wrote two episodes of Star Trek Voyager (though he was not credited on-screen for his contributions) in addition to being an acclaimed novelist and video game script writer.
Alan Brennert wrote an issue of Marvel's 1980 Trek comic, then became a consulting producer on Enterprise under the pen name Michael Bryant. (For some reason Memory Alpha treats Bryant as his real name.)
Specifically, Mike and Kevin Ryan wrote the story for Voyager's "Resistance." Kevin wrote the two Errand trilogies, some comics, and he and MJF cowrote Requiem together also. Also Eric A. Stillwell, who co-wrote "Yesterday's Enterprise" and "Prime Factors," is a co-author with DRG3 and Armin Shimerman of The 34th Rule.
I can’t believe that people forgot about Captain Kirk himself—-William Shatner! He’s got story credit for Star Trek V, and then he wrote, with the Reeves-Stevens, his line of 24th century Kirk adventures.
Howard Weinstein wrote "The Pirates of Orion" and then went on to write three TOS novels and three TNG novels. And in addition to his other works, we mustn't forget David Gerrold's ST nonfiction.
Another writer of an animated episode was Walter Koenig, who wrote an issue of DC's Trek comic (I think that was the extent of his fictional literary trek output). My guess is - depending on how you factor in issues of the comic - Mr. Friedman's overall output surpasses Mr. David's
Ira Steven Behr & Robert Hewitt Wolfe wrote Legend of the Ferengi. I'm still not sure how to describe it as it isn't a novel or a reference work. A collection of short stories? Behr also wrote the earlier The Ferengi Rules of Acquisition.
Well, looking over Wikipedia's comprehensive list of Star Trek Novels, which is a little hard to quickly count (they double up cells on the spreadsheet when the same writer wrote consecutive books, and some miniseries are listed twice, so I'd have to go through it manually and can't just count the times a name appears on the page using the "Find" feature in my browser) but I can use to get a sense of the TrekLit oeuvre, it seems like Diane Carey has written and co-written the most Star Trek novels, which sounds right to me.
According to Memory Alpha Peter David has written 48 novels, while Diane Carey has "only" written 29.
It's that damn doubling up. PAD was only listed once on Wikipedia for all the New Frontier novels, and Carey got a lot of duplicates because of being involved in duologies, miniseries, and numbered novelizations.
D.C. Fontana also wrote the novelization for "The Questor Tapes". Diane Duane's original Trek characters feature in "The Kobayashi Alternative" text-based computer game. Walter Koenig, who scripted a TAS episode, also did a diary about the making of TMP, called "Chekov's Enterprise". His Trek comic was called "Chekov's Choice". Larry Niven (TAS) co-wrote a comic strip sequel, "The Wristwatch Plantation", as a sequel to "Slave Weapon". Michael Pillar's "Fade In: The Making of 'Star Trek Insurrection' - A Textbook on Screenwriting from Within the Star Trek Universe" was finally published posthumously. Writer of TNG's “The Inner Light”, Morgan Gendel, self-published a comic sequel called "The Outer Light". Surname is Flinn. The opening chapter of "The Fearful Summons" actually novelises the original "rounding up the crew" opening that he had scripted for ST VI, which was dropped and thus never filmed.