Tolkien’s posthumously published mythology edited by Christopher Tolkien in 1977 is The Silmarillion. It was published four years after J.R.R. Tolkien’s death and assembled from a large body of drafts, notes, and revised texts.
The book presents the creation of the world, the history of the Ainur, the First Age wars against Morgoth, and later events involving Númenor and the Rings of Power. Its central narrative includes the Silmarils, three jewels made by the Elf Fëanor.
Christopher Tolkien had to organize material that Tolkien had never prepared as a final, unified manuscript. As a result, The Silmarillion is more mythic and compressed than The Hobbit or The Lord of the Rings. It is not a conventional sequel: it functions as a deep historical and cosmological foundation for Tolkien’s better-known stories.