I think this is off topic, and that it's Literature Stack Exchange's version of a problem Role-Playing Games Stack Exchange resolved in 2012: real-world research questions.
I'd like to summarise the issue briefly, so you can check if there's parallels for yourself.
On RPG Stack Exchange we deal with tabletop roleplaying games like Dungeons & Dragons, the kind you play with pen and paper and dice. Subjects like boats, finance, economies, medieval history, modern technology, and geography get used in those games. So, people started asking us directly about those topics: they'd ask us about real-life medieval boating or the 1930's USA economy or other stuff which frankly had nothing to do with any of our expertise in role-playing games.
Something seemed wrong about that. We weren't meant to be Anything At All Stack Exchange. There were sites like History.SE for questions like that boating one. We weren't sure where to draw the line until 2012, and I'll get to the line we drew in a moment.
Literature has some risk for that too: “this thing showed up in a book, so I'll ask about it on literature” potentially enters domains requiring expertise totally unrelated to literature expertise. Was Mark Twain actually almost a millionaire twice over, before he became famous? was an early borderline question that made me concerned Literature might eventually experience this very phenomenon (though that question seemed to be received OK and may not itself be representative of this issue).
Here's where RPG.SE drew the line: we decided to only accept questions that were materially related to RPG expertise. Our on topic help now sports the following passage:
Questions about a general real-world topic such as history, geography or economics, whilst relevant to RPGs, may be off topic if they are not RPG-centric (or better belong on another Stack Exchange site, such as History). A good rule of thumb is to ask yourself:
Would an RPG expert give me a better/different/more specific answer to this question than a Historian, Geographer, etc?
If yes, then feel free to ask it here.
This means “how does the F-22 fighter jet work?” is off topic and should be asked on Aviation SE instead, but “how can I model the F-22 for this pilot character in Dresden Files RPG?” is on topic.
We adopted this from Game Dev Stack Exchange, which has a very similar passage in their own on topic help to handle their own issue of non-game-related art, music, and programming questions.
I don't know where you'd draw the line on Literature Stack Exchange, though, and it might take a different formula instead. A rule of thumb of “Would an avid book reader or literary analyst give me a better/different…” might not cut it for being clear enough.
FYI: a conversation some of us had about this in chat.