The first version of the story is the Tale of Tinúviel, which was written in 1917 and published in The Book of Lost Tales. During the 1920s Tolkien started to reshape the tale and to transform it into an epic poem which he called The Lay of Leithian. He never finished it, leaving three of seventeen planned cantos unwritten. After his death The Lay of Leithian was published in The Lays of Beleriand, together with The Lay of the Children of Húrin and several other unfinished poems. The latest version of the tale is told in prose form in one chapter of The Silmarillion and is recounted by Aragorn in The Fellowship of the Ring. Furthermore, it was the model for "The Tale of Aragorn and Arwen", which is told in the appendices of The Lord of the Rings.

"Tolkien was a master world builder and The Silmarillion is the result of decades of work. It's heart warming to see Tolkien's son, Christopher, take up the work of his father and faithfully produce and publish unfinished works so that Tolkien's fans could benefit." - RCS

Inspiration

The Tale of Beren and Lúthien was regarded as the central part of his legendarium by Tolkien. The story and the characters reflect the love of Tolkien and his wife Edith. Particularly, the event when Edith danced for him in a glade with flowering hemlocks seems to have inspired his vision of the meeting of Beren and Lúthien. Also some sources indicate that Edith's family disapproved of Tolkien originally, because he was a Catholic. On Tolkien's grave, J. R. R. Tolkien is referred to as Beren and Edith is referred to as Lúthien.

The tale of Beren and Lúthien also shares an element with folktales such as the Welsh Culhwch and Olwen, maybe its main literary inspiration, and the German The Devil With the Three Golden Hairs and The Griffin—namely, the disapproving parent who sets a seemingly impossible task (or tasks) for the suitor, which is then fulfilled. The hunting of Carcharoth the Wolf may be inspired by the hunting of the giant boar Twrch Trwyth in Culhwch and Olwen or other hunting legends. The quest for one of the three Silmarils from the Iron Crown of Morgoth has a close parallel in the search for the three golden hairs in the head of the Devil. The sequence in which Beren loses his hand to the Wolf may be inspired by the god Tyr and the wolf Fenrir, characters in Norse mythology. Tolkien also got inspiration from the great love story of Romeo and Juliet.

Beren and Lúthien standalone book

The story is also to be published as a standalone book edited by Christopher Tolkien under the title Beren and Lúthien on 1 June 2017, being pushed back from its original publication date of 4 May 2017. The story is one of three contained within The Silmarillion which Tolkien believed warrants its own long-form narrative, the other two being The Children of Húrin and The Fall of Gondolin. The book is illustrated by Alan Lee and edited by Christopher Tolkien, in much the same way as the standalone version of The Children of Húrin (2007) in that it draws from different, often incomplete, versions of the story written by Tolkien to form a complete narrative with minimal editorial intrusion.

- Wikipedia