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. Many of the tales within are retold in The Silmarillion, albeit in modified forms; the work also contains a summary of the events of The Lord of the Rings told from a less personal perspective.
For anyone who's read The Lord of the Rings and The Silmarillion and wants more, this is an excellent next read. More detail on tales already told and some fascinating new bits.
