"The Gold Bug" is a personal favorite of mine, despite the offensive portrayal of the African-American character Jupiter.
I guess it belongs in the detective-mystery genre in that it involves breaking secret codes and finding buried treasure.
What I liked about it was the detailed method used by Legrand to break the pirate's code and then interpret it to locate the booty.
Cool story, and still entertaining over a hundred years after it was written!
CyrusThePersian