the key is balance. If a book doesn't feel enough like Star Trek, or if it gets certain things about it wrong, then that can alienate readers. Not to mention that a number of original-SF writers, let alone "literary" ones, tend to see tie-in writing as slumming, so they might look on a Trek novel just as a quick-and-dirty way to make a buck and not put a lot of care into it, if they bothered to do it at all. The best tie-in writers for a given franchise are generally fans of it, people who really know it well and care about it and are willing to put their best work into a tie-in novel about it. You can be an accomplished original/literary writer and love Trek and thus produce really top-notch Trek novels -- but if you're a hugely acclaimed, accomplished author who's never been much of a Trek fan...
and doesn't have strong feelings about it, then your attempt to produce a Trek novel might not work very well as either a Trek novel or a self-contained literary work. After all, good writing entails passion toward your subject.
The mention of Peter David a few posts before, puts me in mind of another possible background for a good tie-in writer. Mr David was an established comic book writer for some years before becoming a go-to Trek auther in the early-to-mid-90s. A comic book writer works on titles and characters owned by the company; he works witin the established setting. A great comic book writer develops a feel for how to inject originality into the series, and where he has to keep the stakes in the ground. Mr David moved from title to title – X-factor, Specatcular Spider-man, Hulk, etc – which meant that he re-learned "the rules" for each title. That's great on-the-job training for a tie-in writer.
(I have huge respect for his work in comics.)
That, plus Mr David's talent and professionalism, plus his obvious fandom: seems like a good recipe for a Trek-novel writer.
Having said all the above, in fact I have not read any of his Trek books. I've had one TNG book sitting around the house forever, possibly Strike Zone, but have never cracked it open. But I assume his Trek books are pretty good ones.
Christopher, I've interacted with you in the music thread, and read several of your other posts with interest. You are clearly a guy who thinks carefully about stuff. Please accept my assurances that a few posts above, where I basically impled that all tie-ins are crap, I did not have your novels in mind.
Actually, I haven't read a ST novel in several years, but reading your posts has kindled a small curiousity in me, to sample one of yours.
Not a temptation I expected to encounter.