The sense of dramatic tension within the narrative is created by Poe's masterful use of foreshadowing and delay. A prime example of this occurs early in the story, when the narrator explains his presence at the Usher mansion. He reveals that the occupant has summoned him there in a letter of "wildly importunate nature," and that the occupant is an old friend who now suffers a "mental disorder" (298). The combination of the ghoulish scene which the narrator has described and the mysteriously disturbed person who resides there evokes in the reader a morbid sense of curiosity and anticipation, foreshadowing a dangerous future for the narrator, his friend, and even the landscape. Instead of gratifying the reader's desire to know more about this dangerous future, Poe instead veers sharply into a discussion of the inhabitant's character as a child. He continues with the fascinating but apparently meaningless (for the moment, at least) observation that the Usher family...

Where the preceding passages were marked by harrowing descriptions and peppered with dramatic dashes, this paragraph is decidedly dry and straightforward. In fact, the entire paragraph contains only one dash and not a single reference to anything horrific.
This is not the only instance in which Poe juxtaposes mundane and informative passages against those of the highest degree of horror. Towards the end of the tale, for instance, the narrator spends an entire paragraph listing some of his friend's favorite books. This information is directly followed by the tragic declaration that "Lady Madeline was no more" and ghastly revelation of Usher's intention of "preserving her corpse for a fortnight" (307). This narrative technique serves to frustrate (and therefore heighten) the reader's anticipation and sense of dread so that the morbid climax, when it finally descends rapidly on the reader at the end of the story, is as eagerly desired as the happiest of endings.

Though readers are hardly aware of the literary tools that Poe uses to psychologically manipulate them, the tools are nonetheless there and devastatingly effective. Because of his subtlety and mastery in using these techniques, Poe will continue to succeed in enthralling and horrifying generations of readers.

References

Poe, Edgar Allen. The Fall of the House of Usher. Naples, Florida: Trident Press, 2001.