An open source library of BOOKS! Like every book ever! Its an initiative to archive all human writings, don’t tell anyone but you can download the books, and read them, and gain knowledge, for free, craziness.
if you have an e-book reader, or are looking for almost any book in digital form, you MUST check out Anna's Archive. the most amazing digital library in existence. I'd rather give my $$$ to them than any publishing company.
internet archive has a LOT of free ebooks/PDFs, especially public domain but also just lots of older things, even textbooks and picture books. amazing resource
i would go thru any libraries you can access first (for ethical/support yr library reasons) - most libraries have a form or you can go to the front desk to request a book be added to the collections. this works for ebooks too! it’s not a guarantee, but sometimes they say yes
if all else fails, you can also just google “[book name] PDF” and if it’s an older or popular title it will probably be online lol. and if you have ibooks you can then export the pdf to ibooks