The importance of father-son dynamics extends also to the making of this book, and I was particularly interested in a passage on page 302 where Christopher Tolkien expresses his regrets that the Silmarillion as originally published was not better; he reflects on the role played by Guy Gavriel Kay in assembling the texts but in the end takes full responsibility for it himself. I was not surprised to read that the story he feels was worst served is the tale of Beren and Lúthien.
There's also a lot of meaty material on the languages - an essay called the Lhammas and a set of Elvish etymologies, which brought home to me that for Tolkien his invented structure was much more than just Quenya and Sindarin, it also included half a dozen other languages spoken by different branches of the Elves, barely mentioned in the stories. I have dabbled enough in
philology to sense the uniqueness of this achievement - very few sf or fantasy writers come anywhere near Tolkien's level of detail in his invented names and words, and some (eg Robert Jordan) are so bad at it that it's painful.
Apart from that, we have the Fall of Númenor, and yet another rehash of the main text of the Silmarillion. I am looking forward to the next volume which is about the early versions of LotR.