J.R.R. Tolkien’s posthumously published Middle-earth history edited by Christopher Tolkien is The Silmarillion.
Christopher Tolkien prepared the book for publication after his father’s death, and Allen & Unwin released it in 1977. The volume presents myths, legends, genealogies, and historical material concerning Arda, the wider world that includes Middle-earth.
Its sections cover the creation of the world, the angelic Valar, the First Age, the downfall of Númenor, and events leading toward the later histories. Unlike The Hobbit and The Lord of the Rings, The Silmarillion is not a single continuous adventure with one narrative style.
The work was assembled from many versions and unfinished manuscripts. Christopher Tolkien had to select, arrange, and sometimes reconcile conflicting texts, so the published book is an editorial construction based on his father’s writings rather than a final manuscript completed by J.R.R. Tolkien himself.