The possibly autobiographical "Eleonora" is a love story which many people assume is about Poe's ill-fated wife (and cousin, who he married when he was 26 and she was 13), Virginia.
The source of the comparison lies on the narrator's similar situation: He's a man who falls in love with his cousin in the Garden-of-Eden-like "Valley of the Many-Colored Grass." Shortly after, in a predictably Poe-like fashion, his object of affection becomes fatally ill and begs the narrator to never leave the valley they fell in love in, and to never love another. He promises he will never leave and never remarry, and then proceeds to do exactly that not long after she dies.
The most improbable element of the story: Eleonora returns from death to give her thumbs-up on the whole ordeal ("Thou art absolved for reasons which shall be made known to thee in Heaven."). Was his real life wife this forgiving? No wonder he married the chick!