The best mystery I read was "The Pit & the Pendulum." It was the best because in my opinion, it was the most suspenseful out of all of the stories. Also, it was the most unique. It wasn't just your typical mystery. The author(Edgar Allen Poe)made it really suspenseful which made me want to keep reading. That is what made it the best.
Great mystery short story starter: mysterious notes start appearing around a school and students start to disappear