Which Tolkien work was published posthumously in 1980 from edited writings about Middle-earth?

Unfinished Tales was published posthumously in 1980, edited by Christopher Tolkien from writings J.R.R. Tolkien left behind. The collection expands stories and historical episodes from Middle-earth that are only briefly mentioned elsewhere.

Its material ranges from the First Age through the Third Age, including accounts involving Númenor, the wizards, and the history of the Rohirrim. Christopher supplied editorial notes to explain variants and incomplete passages.

The title is literal: many pieces remain fragmentary or exist in competing forms. Unlike a single finished novel, the book allows readers to see Tolkien's creative process and the changing versions behind his published narratives.