The books were discontinued by the author's publisher, Dell Books following the Toho Vs. Morrow legal ruling and a dramatic rise in cease-and-desist letters sent by Paramount
Farrand seems to have continued to publish nitpicker books, but only with the explicit consent of the various studios involved. Presumably Paramount declined to give that consent, hence why the books remain incomplete.
You can read the author's statement here in full.
My current writing career ended sometime around noon last Monday when
my agent Steve Ettlinger called. (Quite a way to start the week, eh?)
...
Here's the facts as I know them. Apparently, there was an unauthorized
movie guide for Godzilla that was due to be released in conjunction
with the new movie. In mid-April, the copyright and trademark owners
of Godzilla won an injunction against the publisher of the
unauthorized guide and stopped it's release.
Unfortunately, the judgment in the case was written quite broadly.
At the same time, Paramount has been stomping through the unauthorized
publishing niche--as they did on the web several months back--firing
off letters to anyone and everyone that they feel might be infringing
on their copyrights. A few weeks ago, I spoke with a fellow author
whose publisher had yanked his DS9 trivia book after he had already
turned in the manuscript.
...
Dell has canceled the Star Wars Nitpicker's Guide and has stated that
it has no interest in publishing any other Nitpicker's Guides.
However, as far as I know, Dell will continue to sell the current
spate of Guide. But . . . my relationship with them has ended.
And . . . it seems unlikely that another publisher would be willing to
take on the risk--given the atmosphere of the market and other current
lawsuits.
