Project Gutenberg
There is a web page that lists books for free, and this page is free to access. It’s called the Project Gutenberg web page, and it lists books that have expired copyrights. You can find all the classics, plus a lot of books that you would not expect.
The books you can find on this page are older, sure. The most recent ones are from the early 1920’s, but still there is a lot to be had. It is also a wonderful look back into history.
You can learn a lot from the Project Gutenberg web page, and the books available on it.