J.R.R. Tolkien’s The Silmarillion was published posthumously in 1977.
Tolkien died in 1973, leaving a large body of unfinished and variant material about the mythology of Arda. His son Christopher Tolkien edited this material into a publishable volume, with assistance from the fantasy writer Guy Gavriel Kay. The Silmarillion appeared four years after Tolkien’s death.
The book presents the creation of the world, the history of the Valar, and the tragedies of the Elves in the First Age. It is therefore much more mythic and chronicle-like than The Hobbit or The Lord of the Rings.
The publication date is sometimes confused with Tolkien’s death date or with the dates of his two famous novels. Unlike those books, The Silmarillion was assembled and released after his lifetime from decades of developing drafts.