Adventure, Gothic Fiction, Mystery
The "mystery" part of the genre of The Hound of the Baskervilles is pretty obvious: who killed Sir Charles Baskerville? Who is trying to kill his heir, Sir Henry? These questions are the plot engines of the novel, and it's the job of Holmes and Watson to provide the answers. As for "adventure," well, there's a game of wits between Holmes and his murderous opponent Stapleton, which involves dangerous bogs, false identities, secret dogs, and hidden love affairs. That sounds like adventure to us.
Can we attach a "Gothic" label to a detective story like The Hound of the Baskervilles? We think we can make a good case for it. Gothic fiction is supposed to frighten you; it also, characteristically, has dark, over-the-top imagery, melodrama, maidens in peril, things going bump in the night, madness, and supernatural elements. Think Tim Burton movies (Corpse Bride, Sweeney Todd) and Edgar Allan Poe (almost everything he ever wrote).
The story of Hugo Baskerville getting his throat torn out by a beast from hell after locking up a woman in his castle? Totally Gothic. Or how about this description from Watson of his first approach to Baskerville Hall:
Through the gateway we passed into the avenue, where the wheels were again hushed amid the leaves, and the old trees shot their branches in a sombre tunnel over our heads. Baskerville shuddered as he looked up the long, dark drive to where the house glimmered like a ghost at the farther end. (6.42)
Give us a sec—we'll be out from under the covers in a minute.
In some ways, Holmes is the antidote to the Gothic elements in the novel. He's too practical and grounded to get carried away by the creepy atmosphere. The bright lights and modern atmosphere of London are comforting to the reader after the foggy, scary bogs of Dartmoor.