Odd: it got one of my vanishingly rare "Outstanding" votes.I haven't read all Trek books but my guess is Second Self by Una MacCormack.
I explicitly recused myself from weighing in on one of McCormack's other works, Last Best Hope, but I also made it very clear that it was not because I considered it poorly written, or otherwise objectively bad, but simply because I intensely dislike unmitigated tragedies in which disaster is absolutely unavoidable. That she did an exceptionally good job with the unenviable task she'd been handed doesn't change the fact that upon finishing it, I wished I could un-read it.