https://en.wikipedia.org/wiki/Ancient_literature

Other Internet sources might claim other book(s) as being the oldest book(s), use a search engine.

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http://www.kingjamesbibleonline.org/Genesis-6-4/

Something to think about maybe in relation to the "Epic Of Gilgamesh", the books by Homer "The Iliad & The Odyssey", there is also Vergil's "Aeneid"  and many other books from India, Egypt and other places.

Let us not forget about such as the "Tuatha Dé Danann" people:

https://en.wikipedia.org/wiki/Tuatha_D%C3%A9_Danann

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There is even stuff such as:

https://en.wikipedia.org/wiki/Ragnar%C3%B6k

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Creation stories:

https://en.wikipedia.org/wiki/List_of_creation_myths

http://www.gly.uga.edu/railsback/CS/CSIndex.html