Which Tolkien book was published in 1977 after editing by Christopher Tolkien?

The Tolkien book published in 1977 after editing by Christopher Tolkien was The Silmarillion.

Christopher Tolkien assembled and edited the posthumous volume from his father’s extensive writings about the mythology and history of Arda. The book was published on 15 September 1977, four years after J.R.R. Tolkien’s death. It presents creation stories, accounts of the Valar, and narratives from the First Age, including the wars against Morgoth.

Unlike The Hobbit and The Lord of the Rings, The Silmarillion is not a single continuous novel centered on one traveling group. It is a collection of interconnected mythic histories, genealogies, and tales, including “Of Beren and Lúthien” and “Of Túrin Turambar.”

Christopher’s editorial role involved selecting, arranging, and sometimes reconciling variant drafts. The published book therefore represents a carefully constructed presentation of Tolkien’s unfinished materials, rather than a final manuscript completed by Tolkien himself.