J.R.R. Tolkien’s posthumously published collection of mythological writings edited by Christopher Tolkien in 1977 was The Silmarillion.
The Silmarillion was published on 15 September 1977, four years after Tolkien’s death. Christopher Tolkien edited and arranged material his father had developed, revised, and expanded across many decades. The book presents the creation of the world, the history of the Valar and Elves, the rise of Morgoth, and the events that shaped later ages of Middle-earth.
Its five major parts include the Ainulindalë, Valaquenta, Quenta Silmarillion, Akallabêth, and Of the Rings of Power and the Third Age. The central Quenta Silmarillion recounts the wars over the Silmarils, jewels made by Fëanor.
The book is not a conventional novel with one continuous narrative. It is a mythological history assembled from multiple forms and periods of Tolkien’s writing. The History of Middle-earth is a separate twelve-volume editorial series, while The Children of Húrin is a later standalone publication.