Okay, here's the dirty little secret of the tie-in business:
It doesn't matter who writes the books.
I mean, it matters to some degree, in the sense that someone who doesn't know the franchise shouldn't write the books (Greg Cox and I can tell horror stories about the hiring of two writers who obviously did not know Farscape to write Farscape novels, to give one example), but not to the same extent as it would in non-tie-in fiction.
Yeah, I've read some awful tie in fiction, so I'd argue the author does matter actually. Thankfully Trek has mostly avoided that.
Speaking personally I DO shop as much based off the author as anything else. Just slapping 'Star Trek' on a book will not ensure I buy it.