After searching for question and tags related to Sherlock Holmes, I was a little surprised to find that none really exist. I suppose this is because Sherlock Holmes is not exactly science fiction or fantasy. But then, where could I go (on Stack Exchange) to ask about the Sherlock Holmes novels and short stories?
The Movies and TV SE has a Sherlock tag, but it hardly seems appropriate to ask about the written works there.
There was apparently a Literature SE, but it failed a long time ago.
It seems quite likely that many people on this SE would be interested in Sherlock Holmes questions in the same way they enjoy Doctor Who or Harry Potter questions.
Allowing Sherlock Holmes and other mysteries might be a slippery slope towards allowing all fiction, but it seems like you're missing a huge fan base.