Which 1977 book did Christopher Tolkien edit and publish after J.R.R. Tolkien’s death?

Christopher Tolkien edited and published The Silmarillion in 1977, after J.R.R. Tolkien’s death.

The Silmarillion presents the mythology and history of Tolkien’s invented world from its creation through the First Age and beyond. It includes the creation of Eä, the rebellion of the Ñoldor, the wars against Morgoth, and later accounts connected with Númenor and the Rings of Power.

J.R.R. Tolkien left the material in many forms, including drafts, revisions, notes, and incomplete narratives. Christopher Tolkien organized and edited that material into a publishable volume, with assistance from the fantasy writer Guy Gavriel Kay. The result is not a conventional novel like The Hobbit or The Lord of the Rings; it resembles a collection of mythic histories, legends, genealogies, and annalistic accounts.

Unfinished Tales was published later, in 1980. The Children of Húrin appeared in 2007 as a fuller edited presentation of one story. These related books are sometimes confused with The Silmarillion, but they were separate posthumous publications.