hopefully if this book is sucessfull chistopher will publish the longer version of beren and luthien, that was never finished. neither was this tale there are many versions and alternates of passages so this book will certainly be working out a complete text from them just like he did with the silmarillion.
I would like to read the original manuscripts, what tolkien actually wrote, readers of the history of middle earth only get a small amount of this. the only thing published in it's complete form are the book of lost tales, and the lays of belerriand as well as the early sketch of the mythology and the annals.
the most interesting volumes to me are morgoth's ring, and the war of the jewels. being the final version of the silmarillion tolkien worked on until his death, albeit in very compressed form with lots of notes.
then there is that other book coming out about the history of the hobbit, in 2 volumes not written or edited by christopher tolkien but sanctioned by the tolkien estate.
the one book they blocked from being published that i very much wanted to read was Tolkien's translations of the epic old english poem beowulf in prose and verse edited with tolkien's original notes by michael d.c. drout professor of wheaton college massachusetts.
by the the way there is an illustrated hardback edition by alan lee coming out, and i think he does the cover art as well.