The Silmarillion was published posthumously in 1977 as a collection of Tolkien’s mythological narratives.
Tolkien worked on the stories that became The Silmarillion for much of his life. They describe the creation of the world, the angelic Valar, the history of the Elves, the wars against Morgoth, and the downfall of Númenor. Much of the material is set before the events of The Hobbit and The Lord of the Rings.
Tolkien died in 1973 without producing a final published version. His son Christopher Tolkien edited the surviving texts into a coherent volume, making editorial decisions about variant drafts and unfinished passages. The resulting book was published in 1977.
The Silmarillion is not a conventional single-volume novel with one continuous protagonist. It is a mythology and history of Tolkien’s imagined world, written in several styles. That structure distinguishes it from the more directly narrative Hobbit and Lord of the Rings.