Christopher Tolkien books in order
20 books in the catalogue, about 151 hours of reading in all; the shortest takes 3 hours and the longest 9 hours.
20 standalone books in the catalogue.
Standalone books
Sir Gawain and the Green Knight, Pearl, and Sir Orfeo 3.0 h 
The Silmarillion 7.8 h 
Unfinished Tales of Númenor and Middle-earth 9.4 h 
The Book of Lost Tales [1/2] 5.7 h 
The Book of Lost Tales, Parts One & Two 6.6 h 
The Book of Lost Tales [2/2] 7.7 h 
The Fall of Gondolin 5.5 h 
The Lays of Beleriand 7.2 h 
The Shaping of Middle-Earth 7.0 h 
The Lost Road and Other Writings 8.4 h 
The Return of the Shadow 9.1 h 
The Treason of Isengard 9.2 h 
The War of the Ring 8.7 h 
Sauron Defeated 8.8 h 
Morgoth's Ring 8.9 h 
The War of the Jewels 8.6 h 
The Peoples of Middle-Earth 9.1 h 
La Caida de Numenor 6.8 h 
Beowulf: A Translation and Commentary 8.2 h 
Beren and Lúthien 5.5 h