Initiated by Rice University in the United States, it offers open-source teaching materials in fields such as mathematics, physics, biology, and economics, suitable for both students and self-learners.
Free Open University Textbook Platform
Click the "Visit Site" button on this page to open the official OpenStax website, then follow its on-screen instructions.
OpenStax is accessed online through your browser, so there is usually no local installation. Refer to its official site for details.
You can browse comparable reading sites under the e-books category on this site and pick the one that fits you.