Answer:
He's reading to try to distract himself from the grief of losing a "rare and radiant maiden" named Lenore. ... Perhaps the gentle knocking on the door causes him to hope that it's Lenore, and he has to tell himself otherwise in order to quell the likely disappointment that reality will bring him.
I believe the correct answer is hyperbole.
Hyperbole is a rhetorical figure of speech which show some kind of exaggeration - in this particular example, the hyperbole is found in the words 'an hundred years.' This is so because the poet won't really spend a hundred years to praise the woman's eyes, but is rather exaggerating a bit.
