Any discussion of Edgar Allan Poe's important works has to include "The Gold Bug." This mystery won the grand prize in a writing contest and earned Poe the title of "father of the modern detective story." It is probably one of his most successful works. "The Tell-Tale Heart," "The Cask of Amontillado," "The Masque of the Red Death," and "The Fall of the House of Usher" are some of his most important short stories. No author captures the slow descent into horror or insanity in quite the way Poe did. These stories are frequently taught in high school literature classes.
In addition, Poe was an established poet. "The Raven" is one example of his poetic skill. While it, too, highlights the darkness of mental instability, some of his best poems, while sad or tragic, have an undeniable beauty. These would have to include "Annabel Lee," "Helen," and "Alone."
I have included an eNotes link to "The Fall of the House of Usher," and one of the other links actually has Poe works you can read online.