Which Tolkien book was published in 1977, four years after his death?

The Silmarillion was published in 1977, four years after J.R.R. Tolkien’s death.

Tolkien died on 2 September 1973, leaving behind extensive writings about the mythology of Arda. His son Christopher Tolkien edited these materials into The Silmarillion, which George Allen & Unwin published on 15 September 1977. The book therefore appeared after Tolkien’s death, unlike The Hobbit and The Lord of the Rings.

The volume presents the creation of the world, the rebellion of the Noldor, the history of the Silmarils, and major First Age narratives. Its structure differs from Tolkien’s novels: some sections resemble mythic chronicles, while others are more fully narrated stories.

The Children of Húrin was also published posthumously, but much later, in 2007, as a distinct edited presentation of one First Age tale. The Book of Lost Tales is part of Christopher Tolkien’s later History of Middle-earth project rather than the 1977 volume.