What was J.R.R. Tolkien’s first published Middle-earth work after his death?

The Silmarillion was J.R.R. Tolkien’s first published Middle-earth work after his death.

Tolkien died in 1973, and his son Christopher Tolkien edited The Silmarillion for publication in 1977. The book presents a mythology and history reaching from the creation of the world to the events preceding The Hobbit and The Lord of the Rings.

Unlike a conventional novel, The Silmarillion combines creation mythology, historical narrative, heroic legend, and chronicle-like material. It includes the Ainulindalë, Valaquenta, Quenta Silmarillion, Akallabêth, and Of the Rings of Power and the Third Age. Christopher assembled material from different periods of his father’s writing, so the published volume reflects editorial decisions as well as Tolkien’s original texts.