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human
[LotR] Do the Silmarillion and other books exist in the canon of the universe?

The hobbit and the Lord of the Rings were more or less written by Bilbo and Frodo respectively. Do the other books in the Tolkien universe have canonical authors too?
gpt
Bilbo also wrote The Silmarillion.

Tolkien toyed with other explanations, such as having a 10th century Anglo-Saxon mariner (and descendant of Eärendil) named Ælfwine set sail and wind up on the beaches of Tol Eressëa where he learned all the tales in The Silmarillion from the Elves there. He eventually returns to England and translates the stories to Old English. These other ideas were never finalized and Tolkien never officially made Bilbo the author of The Silmarillion, but his son has commented that he believes his father intended that the tales were written by Bilbo.

The in-universe title given by Bilbo is "Translations from the Elvish" and they are included in the Red Book of Westmarch together with "There and Back Again. And What Happened After." (The Hobbit) and "The Downfall of the Lord of the Rings and the Return of the King" (The Lord of the Rings).