Therin of Andor wrote:
If you noticed, Vonda McIntyre had a falling out with Richard Arnold on the ST IV novelization; it was one of the first books that Roddenberry got him to vet rather than Susan Sackett, IIRC. RA hated the authors adding new material and would mention it at conventions. You can see that, after the sequence with the San Francisco trash collectors (McIntyre makes their lines quotes from a Hollywood script they're writing together), she totally stops adding additional material for the rest of the book. It was also her last book for "Star Trek".
I thought the issue with the Star Trek IV
novelization, since McIntyre talked about this in an interview a few years ago, was that midway through writing the novelization Paramount suddenly wanted an outline for the book, and that McIntyre's response was that she could either finish the book by the deadline or she could stop writing the manuscript and spend her time on an outline, but that she couldn't do both.
Also, I don't know where you're getting this idea that there's no additional material in the novelization after the trash collectors. I distinctly recall that there's a plotline with an FBI agent that goes right up until the end of the book. The reason I remember this is that I was disappointed when I saw the film and there was no FBI agent; I was looking forward to seeing that on screen.