#read2023 The Lost Road and Other Writings, by #JRRTolkien, edited by Christopher Tolkien.
This is volume 5 of the History of Middle-earth, and has the earliest versions of the Númenor story, and an aborted start to a time travel story (the titular "The Lost Road"). It also has the last version of the Silmarillion material before it was put aside to start work on that Hobbit sequel that his publisher wanted (having rejected all of the above projects).
One highlight is seeing the first versions of the battle of the last alliance made famous as the opening of Peter Jackson's adaptation of Fellowship of the Ring - this predated the start of writing of Lord of the Rings by several years! It's the very last story of the Elder Days as Tolkien envisaged it in the mid-1930s: Sauron is overthrown, Gil-galad and Elendil die in the process and ... that's it. Story over! No Isildur, no One Ring, no Third Age.
This book also has the source material for the last chapter of the Quenta Silmarillion as eventually published, since it was the last time that stage of the story was written. It's in a very high-level, summarising style, which is why, if you're familiar with it, the decades-long War of Wrath is treated so very briefly. And old Ancalagon the Black gets but one sentence.
The last part of the book has 60-odd pages of etymological stems in Elvish languages and how they developed. Not exactly gripping reading for non-linguists, but there are little gems here and there about things that never show their face elsewhere, new aspects to known characters, or creatures that don't appear in a story.