The Internet Archive is a 501(c)(3) non-profit library. Founded in 1996, their mission is to provide Universal Access to All Knowledge. They collect published works and make them available in digital formats.
It is a San Francisco–based nonprofit digital library with the stated mission of "universal access to all knowledge." It provides free public access to collections of digitized materials, including websites, software applications/games, music, movies/videos, moving images, and nearly three million public-domain books. As of October 2016, its collection topped 15 petabytes. In addition to its archiving function, the Archive is an activist organization, advocating for a free and open Internet.
The Internet Archive allows the public to upload and download digital material to its data cluster, but the bulk of its data is collected automatically by its web crawlers, which work to preserve as much of the public web as possible. Its web archive, the Wayback Machine, contains over 306 billion web captures. The Archive also oversees one of the world's largest book digitization projects.
They have chess books, lots and lots of chess books! In some cases in order to read the books you will have to have an account, but it's free. Just register your e-mail address and a password. By the way, I created a separate e-mail account just for chess related material. You will need an account because some books can only be accessed by “borrowing” them for a period of 14 days.
Here is the LINK to the search for chess books.