Star Trek: 10 Things You Didn't Know About Dr Leonard 'Bones' McCoy
4. McCoy's Adventures While Trapped In Earth's Past
There have been countless non-canon depictions of McCoy in video games, books, and more, but one of the most compelling was a novel by David R. George III that was (succinctly) titled Star Trek: The Original Series: Crucible: McCoy: Provenance Of Shadows.
David had previously worked as a writer for Star Trek Magazine and the Voyager episode Prime Factors. He created the Crucible series to celebrate the 40th anniversary of The Original Series. It was a trilogy that focused on the Original Series episode The City On The Edge Of Forever from the perspectives of the three main characters from the episode.
McCoy's novel in the series explored the episode's two different timelines. One in which Kirk's love interest, Edith Keeler was killed in front of him (just like what happened in the original episode), but also another where McCoy saved her, causing a butterfly effect that removed the Federation from history.
The alternate universe segments of the book give us a rare look at McCoy's character on his own. At first, he tried desparetely to contact the future for help, but over time gradually started to accept that he was alone. Eventually, he settled down after working through some of his past regrets. The story was non-canon, but it gave some interesting context to McCoy's life in the alternate reality from the original episode.