Check out the World EBook Fair' site (not free, but reasonable) for FREE downloads from the Gutenberg Project, the first producer of free eBooks. There is a children's collection of classics and others (no longer copyright protected) -- photos of the front covers show wonderful old illustrations from my mother's childhood. I guess the covers promote story, which we'd download (text.) Maybe also available in audio with human reader or digital text to voice. Interesting.
Even more interesting to me (a former Gov Docs Librarian) is how government document collections are also available through the World eBook Fair. Examples: