Can I include questions about detective stories in this site? If not, on which site can I post them?
Maybe. As taken from this question;
- If it's marketed as SF, it's on-topic.
- If magic, futuristic science or technology, alternate history, or other sf-nal concept is an important part of the overall plot, it's on-topic. (Alice in Wonderland, Clockwork Orange, etc.)
- If the question is specifically about an sf-nal element, even if it's only a minor part of the work, it's on-topic.
- If it's set in an on-topic universe, it's on-topic.
- If you're not sure it's SF but you think a good case can be made for it, it's on-topic.
- If there is a minor supernatural element (e.g. a fortune teller's prediction comes true, or someone sees a ghost, or a story for children involving anthropomorphic animals) but it's just a throwaway plot element that's not particularly relevant to the question, it's off-topic.
So if the story contains elements of science fiction or fantasy, you might be able to ask it here.
If the story in question has been turned into a film or TV series, you may want to take a look at Movies.SE and try there.
Are "detective stories" on topic?
Per the site's FAQ, detective stories are not on topic for the site unless they contain elements that are science fictional or in some way fantastical:
What topics can I ask about here?
Science Fiction & Fantasy Stack Exchange is for questions targeted towards science fiction and fantasy enthusiasts. This includes questions about:
- Plot, character, or setting explanations
- Historical or societal context of a work
- Behind-the-scenes and fandom information
- Story identification
- Franchise/series reading or viewing order
You may wish to note that this question specifically asked about whether the Sherlock Holmes stories are on topic. The overwhelming vote was that they are not.
Where can I ask them?
It depends if they're Sci-Fi or Fantasy detective stories or not. For example Leviathan Wakes by James S. A. Corey is a Detective story set in a Sci-Fi context. Your traditional Agatha Christie detective novels would be off topic.