What is the title of J.R.R. Tolkien’s posthumous 1977 mythology book?

J.R.R. Tolkien’s posthumous 1977 mythology book is The Silmarillion.

The Silmarillion was edited and published by Tolkien’s son Christopher Tolkien four years after Tolkien’s death. It presents stories about the creation of the world, the Ainur, the Elves, the wars against Morgoth, and the history of the great jewels called the Silmarils. Much of its material reaches far earlier in Middle-earth’s chronology than The Hobbit or The Lord of the Rings.

Tolkien worked on related legends and drafts throughout his life, but he never completed a final publishable version of the entire collection. Christopher Tolkien therefore had to select, organize, and sometimes reconcile writings from different periods. The result is a designed literary compilation rather than a manuscript Tolkien had prepared for publication in that exact form.

The title is sometimes confused with Unfinished Tales, another posthumous collection edited by Christopher Tolkien. Unfinished Tales appeared later, in 1980.