The title of J.R.R. Tolkien’s posthumously published mythology edited by his son Christopher is The Silmarillion.
The Silmarillion was published in 1977, four years after Tolkien’s death. Christopher Tolkien organized and edited the materials left by his father, working with drafts, revisions, notes, and incomplete texts. The result is a collection that presents the mythology and history underlying The Hobbit and The Lord of the Rings.
Its opening section, the Ainulindalë, describes the creation of the world through music. Later sections recount the history of the Valar, the Elves, the Silmarils, Númenor, and the events leading toward the Third Age.
The book is not a conventional novel with one continuous narrative. Its forms include myth, chronicle, legend, and annal. Unfinished Tales is a separate posthumous collection, while The Children of Húrin is a later standalone presentation of one story from Tolkien’s wider mythology.