The Return of the King is but a small portion of Tolkien's exhaustive writing on Middle Earth. In addition to being the third volume of The Lord of the Rings, it pulls from a deep well of history written well before Tolkien started on the trilogy. The Hobbit, for instance, serves as a prequel of sorts, and tells the story of how Frodo's uncle, Bilbo, came to possess the One Ring.
There is also Tolkien's magnum opus The Silmarillion, which Tolkien worked upon for his entire life, and which was edited and published posthumously by his son Christopher Tolkien. The Silmarillion is the keystone to Tolkien's Middle-Earth writings, but unlike The Lord of the Rings or The Hobbit, it is not...
