J.R.R. Tolkien's novels of Middle-earth - The Hobbit, The Lord of the Rings trilogy, and The Silmarillian - have become some of the most famous, and most beloved, literary works of the twentieth century. And the Lord of the Rings films by director Peter Jackson have re-ignited interest in Tolkien and his works, as well as introduced his stories to a new generation of fans.

Even if you've never read the novels and have only seen the films, you know that the world of Middle-earth is a complicated one. Tolkien took great care in representing this world, from...