The Fall of the House of Usher

In the short story, the house is described as very mysterious and dark home. The narrator attempts to lighter the mood of the Usher by singing songs, playing music and by telling him many stories. during the death of the Usher's sister, she reappears. This caught Usher completely by surprise and in shock he dies as the house falls into pieces. The entire story seemed extremely strange to me. I feel that through the whole story, the man is very deranged and not mentally sane.