One example of irony that Poe uses in this poem is the tortured scholar himself. We learn that the man suffering for Lenore is a scholar. We know this because he is surrounded by books, as well as due to the fact that he has a bust of Pallas. Therefore, this is an educated, reasonable, and probably very logical man.
Therefore, it is ironic that this is the man that ends up in such a diminished and sad state. Moreover, the thing that tortures him is not particularly elevated. He suffers because of his love for a woman. Moreover, even though he is extremely clever and educated, his sanity is completely destroyed by a talking raven. The ending is an ironic outcome for the learned scholar.