1930: Orpheus: Myths of the World.

Here's a book published in 1930, thus entering the public domain on January 1 2026:

Orpheus: Myths of the World
by Padraic Colum
(illustrated by Boris Artzybasheff)
Internet Archive

Padraic Colum was a well-known reteller of folktales and myths; you can find out more about him at Wikipedia: Colum. Many of his books are already in the public domain; here's a list.

This book has a wide range of stories, some from unusual sources; the Jewish legends are especially intriguing (they are both about the angel Samael) — although Colum does not, unfortunately, provide a bibliography of his sources. The 20 illustrations are wonderful; you can read more about the illustrator at Wikipedia: Artzybasheff.

Here is an illustration for the Polynesian creation legend:

And here is the Celtic legend of Pwyll:

And that's the image you can see on the cover of this 1996 edition: