Here are the particulars from the Tolkien Society:
https://www.tolkiensociety.org/2018/...-be-published/
It will be interesting to see how much of this will be just reprinted material from previous Tolkien sources. I have to hand it to Christopher Tolkien, though -- he is quite cagey, lengthening the family copyrights on much of his father's corpus long after its original inclusion in The Silmarillion, published in 1977.
But it will be 304 pages long (must be very LARGE print), and will have Alan Lee illustrations.