There's not much to say about this classic that hasn't been said. It is still one of my favorite poems of all time. They say Coleridge was heavy into opium when writing this, and other works. If he was, it might explain the visions, but regardless, this is a classic piece of literature. I have read this dozens of times and it's great, but when combined with Gustav Dore's illustrations, it is nothing short of magnificent. I have many of the classics done by Dore, and they are all great, but this is some of his finest work, in my opinion.
If you haven't experienced either The Rime of the Ancient Mariner, or the work of Dore, open up your wallet and get this. It's that good.