Project Gutenberg (PG) is a volunteer effort to digitize and archive cultural works, to “encourage the creation and distribution of eBooks”. It was founded in 1971 by American writer Michael S. Hart and is the oldest digital library. Most of the items in its collection are the full texts of public domain books. The Project tries to make these as free as possible, in long-lasting, open formats that can be used on almost any computer. As of 23 June 2018, Project Gutenberg reached 57,000 items in its collection of free eBooks. The releases are available in plain text but, wherever possible, other formats are included, such as HTML, PDF, EPUB, MOBI, and Plucker. Most releases are in the English language, but many non-English works are also available. There are multiple affiliated projects that are providing additional content, including regional and language-specific works. Project Gutenberg is also closely affiliated with Distributed Proofreaders, an Internet-based community for proofreading scanned texts.
They provide trade-free books! No trackers, no ads (except the ad for their hosting provider) and rely on donations. Worth mentioning is that their eBooks are mostly older literary works. Most were published before 1924, with some published in the decades after.