I wanted to read this book after hearing tarkrai's setting of the poem, which turns out to be the chapter headings. I'd thought it was out of print, but I got a paperback copy a few cons back.
It's not the story you might expect from the song. It's a fairly original fantasy story, in its own world, but a pretty generic middle-ages-with-magic setting. The way magic works is original, and interesting, although it's kind of nasty. The actual story is a quest, but not quite the usual one. For the first few chapters, the plot and characters seemed rather hackneyed, but as I got into it, it started to grow on me. I still had a few problems about how believable the most important characters are (one is too competent to really believe, the other too naive), but the story grew on me as the characters themselves grew. There's more actual character development in this novel than in most.
A good read once it gets going. 8 out of 10.