J.R.R. Tolkien’s The Silmarillion first appeared in 1977.
The book was published posthumously by George Allen & Unwin, four years after Tolkien’s death. It presents a collection of connected stories about the creation of the world, the Valar, the Elves, and the First Age of Middle-earth. Tolkien had worked on related mythology for decades, but he never completed a final version for publication.
His son Christopher Tolkien edited the surviving materials and shaped them into the published volume, with assistance from Guy Gavriel Kay. The Silmarillion is not a direct sequel to The Lord of the Rings. It is instead a mythic history that supplies much of the deep background behind later stories.