J.R.R. Tolkien’s 1977 posthumous mythology book is The Silmarillion.
The Silmarillion was edited and prepared for publication by Tolkien’s son Christopher Tolkien, with assistance from the fantasy writer Guy Gavriel Kay. It was published on 15 September 1977, four years after Tolkien’s death. The book presents a broad history of the world of Arda, from its creation through the First Age and beyond.
Unlike The Hobbit and The Lord of the Rings, The Silmarillion is not a single continuous adventure centered on one protagonist. It contains creation mythology, genealogies, legends, and accounts of wars involving Elves, Men, Dwarves, and the first Dark Lord, Morgoth.
The title is sometimes treated as though it refers to one story. In fact, it also names the book’s central subject: the three jewels called the Silmarils, whose creation and theft drive much of its First Age narrative.