Which Tolkien work was published posthumously in 1977, edited by Christopher Tolkien?

The Silmarillion was published posthumously in 1977 and edited by Christopher Tolkien.

The book presents a collection of myths and histories concerning the creation of Tolkien’s world, the Valar, the Elves, the wars against Morgoth, Númenor, and events leading toward the later history of Middle-earth. It is much more concerned with legend, genealogy, and the distant past than with the intimate adventure style of The Hobbit.

J.R.R. Tolkien worked on these stories for decades but did not complete a definitive final version. After his death, Christopher Tolkien selected, arranged, and edited material from manuscripts, sometimes combining different versions to create a readable narrative. The published book therefore reflects both Tolkien’s original writings and Christopher’s editorial decisions.

The title can be misunderstood as referring only to a single story. In fact, The Silmarillion is a layered work made up of several sections, including the Ainulindalë, Valaquenta, Quenta Silmarillion, Akallabêth, and Of the Rings of Power and the Third Age.