I have a sentimental attachment to her books, as the novelizations of II-IV were the first TrekLit that I read back in 1986-87. I tore throughout that trilogy and loved how it fleshed out so much that wasn't on screen. I remember that IV had a lot less "extra", but I didn't realize that was because of licensor crack-down. I recently picked up a used copy of the Duty, Honor, & Redemption omnibus with the intention if rereading almost 30 years later.
From what I recall, the
Duty, Honor, Redemption omnibus updates/alters several plot-elements from the original printings to fit retroactive continuity, such as Sulu's rank getting changed from "captain" to "commander," etc. (Not unlike the updating of Diane Duane's
Rihannsu novels in
The Bloodwing Voyages collection.)
All that "extra" in the Trek III novelization, was that from the script/screenplay? Or did she make it up? Anybody know?
Apart from Saavik being half-Romulan (which comes from material actually filmed for
Star Trek II, but deleted) and all of that backstory, the majority of the "new" expansionary content seen in the
Search for Spock novelization was entirely Vonda, IIRC.
The screenplay for that movie is actually quite tight, with very little filler; probably the leanest of the first six movies. What you see used onscreen is pretty much exactly what was shot -- comparatively very little was trimmed out, versus other movies' editing processes.
All of the material with Scotty returning home to bury his nephew, Sulu getting "demoted" by Admiral Morrow, the crew-situation aboard the Merchantman vessel, Saavik and David's sexual relationship aboard USS
Grissom and
Enterprise, the crystalline alien in the
Grissom science-lab...largely all of this was created by McIntyre for the novel, not Harve Bennett.