"LibreTexts is an ecosystem of connected tools that empower educators to create Open Educational Resources at scale
LibreTexts is the largest centralized open education project and platform online. Founded in 2008 at the University of California, Davis as the ChemWiki, the LibreTexts mission is to unite students, faculty and scholars in a cooperative effort to develop an easy-to-use online platform for the construction, customization, and dissemination of open educational resources (OER) to reduce the burdens of unreasonable textbook costs to our students and society."
Find digital textbooks, build your own textbook adaptive homework, collaboration tools and interactive modules.
A K-12 bookshelf is available within this repository here - https://k12.libretexts.org/Bookshelves