The Tolkien book published posthumously in 1977 as a collection of Middle-earth creation myths and First Age stories was The Silmarillion.
The book opens with the Ainulindalë, an account of creation through music, and continues with the Valaquenta and the Quenta Silmarillion. The central section follows the wars and tragedies surrounding the Silmarils, three jewels created by the Elf Fëanor. Later sections cover the downfall of Númenor and events leading toward The Lord of the Rings.
J.R.R. Tolkien died in 1973, leaving a large and complicated body of related manuscripts. His son Christopher Tolkien edited the material and arranged it into the 1977 publication. The result is closer to a mythology or chronicle than to a conventional novel.
Readers sometimes confuse it with Unfinished Tales, which was published in 1980 and contains separate narratives and commentary. The History of Middle-earth, published in twelve volumes between 1983 and 1996, documents the evolution of Tolkien’s drafts rather than presenting one unified mythology.