Not really. If we discount 1970's Spock Must Die! as an outlier, Bantam's line of original Trek fiction began in 1976, and The Price of the Phoenix was the third book they published in that period, after The New Voyages and Spock: Messiah! So that one was very early in the run. The Fate of the Phoenix was two years later, in '79, and was the fifth-to-last book they did. I agree that they were drawn to books that felt like fanfic, but dwelling on K/S and Mary Sue is oversimplifying what that means. A large part of it was the difference between the authors who were Trek fans doing it out of love and striving to reflect something of the spirit and emotional impact of the show and characters (however awkwardly) and the ones who were professional SF authors for whom it was a paying gig and who maybe didn't capture those more visceral and intangible aspects. (Of course, these days, mostly you have professionals who are also lifelong fans doing the books, so that distinction no longer applies.)
I just picked up 17 TOS books at my local library's books sale and I got the black Bantam The Price of Phoenix and The Fate of Phoenix in the lot. I haven't read them yet.
Count yourself lucky that you haven't read them. Bury them in the back yard where you want nothing to grow.
There's a crazy church in my hometown that's going to have a Koran-burning party on 9/11. If they really wanted to make God happy, they'd burn the Phoenix novels instead.
I suggest folks take all those old phone books that are taking up space, write "Koran" on the cover, and take 'em down. For an added flourish, dressing like SS officers is always a nice touch.
Everyone knows a new Phoenix always arises from the ashes. You really want Part 3 of the trilogy that badly?
I've read probably well over a hundred trek novels. Price of the Phoenix is the only one that I never successfully finished despite several attempts to read it.
They should just wear white bedsheets so no one has to look at their ugly faces. Maybe they'd like to burn a cross too.
According to rumours I heard back in the early 80s, slash fanfic chapter extensions were available on the fannish black market for all four Marshak/Culbreath titles.
Marshak & Culbreath were prominent figures in the fan community themselves, and I believe they did write fanfiction as well as pro fiction, like other early Trek novelists such as Della Van Hise and Jean Lorrah.