There is nothing new
The idea of a book devoted to the evolving story of ‘Beren’ that I ventured to mention to Rayner Unwin as a possible publication would have brought to light much hitherto unknown and unavailable writing. But this book does not offer a single page of original and unpublished work. What then is the need, now, for such a book?
(Beren and Luthien - Preface)
The book includes all or parts of five different versions of the story:
- c1917 - The Tale of Tinúviel [complete]
(published in HoME#2 - The Book of Lost Tales part 2)
- 1926 - Sketch of the Mythology [short excerpt]
(published in HoME#4 - The Shaping of Middle-earth)
- 1925-1931 - The Lay of Leithian [3 excerpts, totaling ~2,800 lines, ~70% of the poem)]
About 400 lines from the c1950 revision are given in an appendix.
(published in HoME#3 - The Lays of Beleriand)
- 1930 - Quenta Noldorinwa [long excerpt]
(published in HoME#4 - The Shaping of Middle-earth)
- c1937 - Quenta Silmarillion [short excerpt]
(published in HoME#5 - The Lost Road and Other Writings and The Silmarillion)
These are followed by a series of short excerpts from Quenta Noldorinwa, Quenta Silmarillion, The Nauglafring (HoME#2), and The Annals of Beleriand (HoME#4) showing what happened after to the characters afterwards.
Significant versions of the story which aren't included:
- The Annals of Beleriand (HoME#4 - The Shaping of Middle-earth))
- The Annals of Beleriand (HoME#5 - The Lost Road and Other Writings)
- The Grey Annals (HoME#11 - The War of the Jewels)
- The unpublished prose version (still unpublished, see below)
As others have noted, it has been said that new text would be included. This was probably the result of people assuming that this would be done in a similar style to how Children of Hurin was done, and that Christopher would finally be publishing the prose version of story that he had talked about in HoME.
Thus at the time when he turned again to the Lay of Leithian (see III. 330), The Lord of the Rings being finished but its publication very doubtful, he embarked also once more on a prose 'saga' of Beren and Luthien. This is a substantial text, though the story goes no further than the betrayal by Dairon to Thingol of Beren's presence in Doriath, and it is so closely based on the rewritten form of the Lay as to read in places almost as a prose paraphrase of the verse. It was written on the verso pages of the text AB 2 of the Annals of Beleriand, and was not known to
me when The Silmarillion was prepared for publication.
HoME#5 - The Lost Road and Other Writings - Part 2, III, pg295)