I do get the impression that OP is looking for Star Trek novels and novelists who are relatively divorced from the kinds of action-adventure-oriented storytelling one finds in many genre stories (...) something like Atonement's thematic depth than Pearl Harbor's frenzy of action and melodrama.
My impression is really that the OP is looking for books that could be considered and enjoyed as great scifi novels independent of the franchise association, i.e. the question is less about quality in an absolute sense and more about quality sans context.
I think both of these are fair characterisations of what I was looking for. Thank you so much to everyone who has made suggestions, especially Sci
for his list. John M. Ford has been a repeated recommendation, so I'll begin with The Final Reflection.