This is by no means an exhaustive analysis of the poem, but basically, the whole thing's about a man who's lost his love and, it's hinted, other people important to him.

He's trying to drown his sorrow in boring old books (as you do!) when the raven arrives and sits on the bust of Pallas (goddess of wisdom). Therefore he assumes the bird might be able to answer some of his cosmological questions.

But it keeps answering 'nevermore' - i.e. you'll never stop being depressed, never see Lenore again, never get on with your life...you get the picture.

Though if I'm helping you with an English essay here, you should consider that the raven is not a literal raven, but a symbol of the man's own depressed psyche.

http://soundcloud.com/coedmusic/bunch-of-noise-a nd-nothing

Unravel

I've been waiting too long now
(To unravel)
I've been waiting too long now
(Waiting...to unravel)

So long to unravel
(On the dock of our nevermore)
I've been slow to unravel
(I've been slow to unvail this thought)