OpenStax
OpenStax is a non-profit initiative of Rice University that publishes peer-reviewed, openly licensed college textbooks. The catalogue covers the standard undergraduate survey courses: biology, anatomy and physiology, chemistry, physics, calculus and statistics, economics, psychology, sociology, US history, and more. Because these are proper textbooks rather than scraped web pages, the writing is careful, the facts are reviewed, and each title is organised into a clean hierarchy of chapters, sections, worked examples, key terms, and end-of-chapter questions. That structure is a gift for retrieval, because it gives you natural, self-contained passages to chunk on rather than having to guess at boundaries.
You can read the books online, download them as PDFs, or take the HTML, and OpenStax also exposes content in structured forms (including a CNXML-based format inherited from its Connexions roots) that is cleaner to parse than a PDF. For a RAG pipeline the practical route is to ingest the per-section HTML, split on the existing section and sub-section headings, and keep the key-term glossaries as their own short entries, which makes for tidy definitional answers.
It is best suited to tutoring and study-support systems, homework helpers, and any education application that needs accurate, introductory-level explanations across many subjects at once. Because the material is pitched at first-year students, it is also a good grounding corpus when you want plain, well-explained answers rather than research-level depth.
The licensing is unusually clean for educational content. Most titles are released under a Creative Commons Attribution (CC BY) licence, which lets you reuse and adapt the text for any purpose, including commercial products, as long as you credit OpenStax. The one thing to check per book is that a small number of titles carry a NonCommercial ShareAlike (CC BY-NC-SA) licence instead, which bars commercial use and requires you to share adaptations under the same terms, so confirm the licence on each title before you build on it. Alongside OpenStax, MIT OpenCourseWare and Wikibooks fill in more advanced and more niche subjects.
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