The remarkable thing is that while the TMP novelization was hardly in the realm of great literature, it's still quite good, especially given that Roddenberry hadn't written a novel before, and hadn't written much prose fiction in years. Indeed, it was a good deal better (or at the very least, better Star Trek) than most of the Bantam-era novels, even those by seasoned authors.
I contrast it with another "first novel," marketed as science fiction, that I fervently wish I could un-read. It is so unspeakably bad that I will not mention the title or author, only that I am truly amazed that it ever made it into the bookstores, let alone that both a sequel and a prequel managed to do so as well. (It makes Marshak & Culbreath's ST novels seem downright literary, by comparison.) If I could ever bring myself to burn a book, this opus I refuse to name by title would be the one; the only reason it is still on my shelf is that I don't want it back in circulation on the used market, inflicting itself upon other unsuspecting readers. And just writing this post gave me a few ideas of how to reclaim the shelf space without discarding it, and without giving it the appearance of being a "guilty pleasure" (guilty, perhaps, but no pleasure).