The first genre we have here is adventure. If you were wondering whether or not that applies here, just check out the story titles. All of them are "The Adventure" of something. Watson himself often refers to the "adventures" that he and Holmes have. But if you don't want to just take Watson's word for it, you can definitely see aspects of a good adventure tale in these stories. Watson and Holmes have the occasional chase sequence, and often get into physical fights with criminals. This is sort of the original buddy-cop show, so adventure is a bit of a given here.
These stories can also qualify as biographies, albeit fictional ones. Despite what some fans say, Sherlock Holmes is a fictional character. (For more on that issue, check out our "Brain Snacks" section.) We're bringing up the biography genre here because of the way that Watson narrates. Watson sets out to narrate the professional career of Sherlock Holmes, one select case at a time. Watson functions as Holmes's biographer in a lot of ways and in terms of genre, the Sherlock Holmes stories can be read as a sort of fictional "life and times" of Sherlock Holmes.
Lastly, we come to our most obvious genre: mystery. The Sherlock Holmes stories basically gave birth to the modern detective story. Granted, there were other examples of detective fiction before Holmes arrived on the scene, most notably Edgar Allan Poe's Dupin stories about a super-smart French detective who could solve seemingly impossible crimes, including one involving a monkey. No, really. Don't believe us? Check out "The Murders in the Rue Morgue." But none of these early detective stories were quite as influential as the Holmes tales.
The stories in The Return of Sherlock Holmes are all classic examples of the mystery genre. We start with an impossible or bizarre case; Holmes works his detective voodoo on the situation; he catches the perpetrator, often the least likely suspect (a feature Law and Order loves to imitate); then Holmes sums up the case and his role in it for everyone, conveniently. Along the way, we also get clues and hints as to what may be going on in the case, though not as much as you'd probably get in a detective novel, where you can often solve the case alongside the hero. Take Agatha Christie stories, for instance. Since the Holmes stories are short stories, we pretty much have to wait for Holmes to provide us with a solution. There's just not a ton of room for hint-dropping and clues here.