As suggested by Wrzlprmft in the chat room, I am posting an answer to see if we can reach a consensus on this question.
I would consider the following types of literature-related questions as off-topic:
- Does work X belong to epoch Y (e.g. Romanticism)? Answers to such questions would normally be based on the date, content and writing style of the work rather than on purely linguistic aspects. By writing style, I here refer to linguistic aspects that go beyond phrase-level or sentence-level aspects.
- Do the works of author X belong to German literature? This means that the question Are the works of Kafka considered German literature? would be off-topic in spite of its 16 upvotes. This question is specifically about "sociopolitical distinction[s]" and the definition of "German literature". Making this question on-topic would require renaming the site to "German Language and Literature Stack Exchange".
- Where can I find the text of work X?
- Did author X really write poem Y?
- When did author X write/publish work Y?
- In German literature, is there a work similar to X in [English/French/Spanish/Chinese/...] literature. Example: What's the “The Anatomy of Melancholy” of German literature?, which as put on hold on 23.12.2018.
- Is literary genre X a subset of literary genre Y? For example, Is a Krimi a subset of a Roman?. Genre definitions are literary questions, not linguistic questions.
- Recommendations for works of literature. For example, Simple but interesting German literature. This question was preserved for historical reasons, stating that '"big list" questions are not generally allowed on German Language and Usage and will be closed per the FAQ.'
Of course, linguistic questions encountered in works of literature are on-topic. For example,
What I have tried to do here is define a dividing line between on "German" in a linguistic sense (on-topic) versus "German" in a non-linguistic sense (e.g. history of literature, sociopolitical questions) when questions somehow involve literature. Questions about lexical and grammatical issues found in works of literature are on-topic.
This is a first attempt to define a borderline between linguistic questions and (non-linguistic) literary questions. Please comment if the distinction is not sufficiently clear. And feel free to add another answer that defines a different borderline. Consensus on questions like this can only be reached through a community effort.