Why fanfic can be so much better than authorised spin-offs
It's always puzzled me as to how officially recognised spin-off novels of my favourite television shows can be so bad, given that the authors presumably have access to the show in ways that amateur fanfic writers can only dream of. But over my holiday last week I read Show Sold Separately: Promos, Spoilers and Other Media Paratexts by Jonathan Gray (2010), and suddenly it all made sense!
"Many paratexts fall under a company's marketing and promotions budget, meaning that the show's creators may have little or nothing to do with their creation, thereby producing ample opportunity for creative disconnects, and for uninspired paratexts that do little to situate themselves or the viewer in the storyworld ... Key to an understanding of any given production culture is an understanding of the culture's shared or contested opinions regarding who and what has value. My argument has been that paratexts have significant value, in and of themselves, but also as components of larger units of entertainment ... A familiar refrain exists throughout my research, which is that successful paratexts tend to be incorporated, while unsuccessful paratexts tend to be unincorporated." (pp. 207-221)
If the showrunners and writers aren't working with the spin-off novelist, and if the writing of the spin-off novel (or comic or episode guide) isn't an incorporated part of the production, then of course it's not going to feel like an organic part of the text. And if the author is writing to a deadline, they're not going to have the luxury of watching and rewatching episodes as fanfic writers do automatically. Nor will they have necessarily been part of fandom discussions that endlessly debate character motivation and obsessively establish canonical and fanonical 'facts'.
It makes sense that fanfic writers, with obsessive knowledge of the show they're writing about, the freedom to take as long as they want to write, and access to the amazing research team that is fandom, are often going to write better stories than guns-for-hire.
As long as the grammar is up to scratch!