The Silmarillion appeared posthumously in 1977 and explores the mythology of Middle-earth.
Tolkien worked on the stories that became The Silmarillion throughout his life. They describe the creation of the world, the history of the Valar, the Elves, the First Age, and the great conflicts involving Morgoth. The book provides the deep historical background behind later works such as The Hobbit and The Lord of the Rings.
Tolkien died in 1973 without completing a final edition. His son Christopher Tolkien edited the surviving manuscripts and arranged them into the book published by George Allen & Unwin in 1977. The result is a constructed collection rather than a conventional novel with one continuous narrative style.
Readers sometimes confuse it with Unfinished Tales, another Christopher Tolkien-edited volume published in 1980. The Children of Húrin, published in 2007, presents a more focused version of one tragic First Age story.