Unfinished Tales (full title Unfinished Tales of Númenor and Middle-earth) is a collection of stories and essays by J. R. R. Tolkien that were never completed during his lifetime, but were edited by his son Christopher Tolkien and published in 1980.
Unlike The Silmarillion, for which the narrative fragments were modified to connect into a consistent and coherent work, the Unfinished Tales are presented as Tolkien left them, with little more than names changed (the author having had a confusing habit of trying out different names for a character while writing a draft). Thus some of these are incomplete stories, while others are collections of information about Middle-earth. Each tale is followed by a long series of notes explaining inconsistencies and obscure points. More: en.wikipedia.org.