The ‘What topics can I ask about here?’ section in the Help Centre currently apologises for being unable to say what is on topic:
Unfortunately, we haven't been around for that long and therefore don't have an authoritative definition of what is and what isn't on-topic. Philosophers have spent centuries debating what literature is. In some circles, the definition of literature has been politicized to exclude certain cultures. We're still trying to find our place in the world of Literature.
However, we can give an incomplete list of topics that we mostly agree are on- and off-topic. Keep in mind that this list is incomplete; if your question isn't here, then you should try asking it on the main site and seeing what happens. Also keep in mind that this is not an authoritative document; should community consensus change, then the advice here could become out of date.
What counts as a work of literature for the purposes of allowed questions on this site? We don't have a specific answer—we're still trying to work this out—but questions have been successfully asked about written stories, comic books, plays, and poetry.
I understand that this level of uncertainty and hedging was needed due to a lack of agreement among the early participants in the site. But the site has now been running for three years and I think that it might be time to remove the apologies and state things clearly.