Here is a selection of websites and resources that I’ve personally found useful in finding free e-books and audiobooks (note that some free books offered at some of these sites may not be family-friendly):
• Project Gutenberg:
https://www.gutenberg.org/ (large selection of primarily [#]public_domain e-books, in various formats)
• LibriVox:
https://librivox.org/ (large selection of public domain, volunteer-read, human-read audiobooks)
• The Internet Archive:
https://archive.org/details/texts (large selection of scanned public domain books, among other things)
• Google Books:
https://books.google.com/advanced_book_search (large selection of scanned public domain books, among other things)
• Hathi Trust Digital Library:
https://catalog.hathitrust.org/Search/Home?type=author&inst= (has a good selection of scanned public domain books, among potentially other things)
•
https://manybooks.net/ (Similar to Gutenberg, but smaller, and somewhat different selection)
• The Church of Jesus Christ of Latter-day Saints:
https://www.lds.org/study/lib?lang=eng (you can get free e-books and audiobooks for scriptures, Church magazines, Church manuals, and many other publications; there is quite a selection; also see the Gospel Library app for mobile devices for another nice way to access e-books and audiobooks)
•
https://www.churchofjesuschrist.org/media-library/ebooks?lang=eng (another place to find e-books on the Church’s website)
• Online libraries that your local libraries let you use (I've used at least one of these for audiobooks; you don't get to keep these forever, but they're free for a while).