What is the subject matter of the poem?

This poem takes as its subject the experiences of a man on a "bleak" December night shortly after the death of his lover, Lenore. On this night, he is attempting to distract himself from his "sorrow for the lost Lenore" by poring over an old book, "a quaint and curious volume of forgotten lore." Suddenly, around midnight, he hears a tapping at his door, but when he opens it there is no one there. He whispers Lenore's name, seemingly in hopes that her spirit has returned. He hears, again, the tapping and opens his window to check: "In there stepped a stately raven of the saintly days of yore." A strange raven who has quite a regal air about him comes through the window and perches upon a bust of Athena in the room.
The narrator, at first, finds the bird sort of charming and curious, and he asks the bird to tell him its name; the bird will only reply, "Nevermore." The narrator asks more questions, each more desperate than the one before as he comes to believe that the bird is some kind of evil prophet sent to tell him that he will never again behold his lover, not even in death. It will only reply "Nevermore" to his queries. In the end, the bird remains on that bust, refusing to leave, and the narrator feels as though the bird's shadow will be cast over his soul for the rest of his days.