Who actually wrote Roddenberry's TMP novelization, anyway? Alan Dean Foster is one name that's been mentioned.
Gene Roddenberry wrote it. It practically screams "first-time novelist with a history in screenwriting who is also incredibly horny and juvenile."
Passages of it in fact do, and that's reason enough to accept that he had a heavy editorial hand in the thing and probably contributed (possibly dictated) long rambling passages. That he was the writer who gave it structure and whipped it into publishable narrative shape is extraordinarily unlikely - there's either a ghost-writer (again, often suggested to be Foster) or an undefatiguably dedicated copy editor somewhere out there who'd doubtless be entitled to co-authorial credit (if he or she would want it).
I've heard the Foster rumour as well, but I've also heard it debunked (though never with Davidcgc's specific points). I could well believe either.