^Well, yeah, I agree that the Marshak-Culbreath books were very... self-indulgent in a lot of ways. But at least they occasionally tried to put their history, psychology, and philosophy degrees to use and work some ideas into their books along with all the fannish indulgence. The Fate of the Phoenix
, their second novel for Bantam, deserves credit for being the first Trek novel to challenge the ethics of the Prime Directive, although, again, it doesn't really embrace the issue, just introduces it, talks about it for a bit, and then moves on to other stuff.
And they did four novels, not three -- The Price of the Phoenix
and The Fate...
for Bantam, The Prometheus Design
for Pocket. Plus they edited the two Star Trek: The New Voyages
anthologies for Bantam, contributing two stories to the second ("Surprise!," co-written with Nichelle Nichols, and "The Procrustean Petard"), and I've heard it alleged that they significantly rewrote the other stories in those anthologies.