J.R.R. Tolkien’s The Silmarillion was published in 1977.
Tolkien died in 1973, so he did not complete or publish the final form himself. His son Christopher Tolkien edited a large body of manuscripts and prepared the work for publication, with assistance from Guy Gavriel Kay. The book appeared four years after Tolkien’s death and presented the mythology of Arda in a compiled form.
The Silmarillion is not a direct sequel to The Lord of the Rings. It is a collection of related legends and histories, including the creation of the world, the history of the Valar, the awakening of the Elves, and the wars over the Silmarils. Its style is more like a mythological chronicle than a conventional adventure novel.
The title refers especially to the three Silmarils, jewels made by Fëanor. The book’s contents draw on material Tolkien revised repeatedly throughout his life.