What is Edgar Allan Poe's The Raven about?

The Raven is ostensibly about a man reading alone in his room. It is December and around midnight when he hears a knock. He thinks that someone is at his door, but it is not. He hopes, irrationally, that the person at the door might be his lost love, who has died. But it is not. Then he realizes that the knocking is coming from the window. In flies a Raven. This raven perches on a bust of Pallas (god of wisdom) above his door. As the man observes the bird, he begins to believe that the bird is a messenger from the other side. He wants the bird to give him comfort, to tell him that there is life after death, that he will be reunited with his true love in death. But, instead, the raven gives him no comfort and the man realizes that grief will be his companion for the rest of his life.