Textbooks should be free! This includes: coursebooks; formal manuals; instruction in a specific subject. For school or personal enrichment.
Archive.org – Opensource Textbooks: Students, invest your money into education, not paper.
BC Campus – Open Textbooks: For educators and learners. All books can be edited for your liken. Free. Awesome.
Boundless: Educational literature items, quizzes, and more. Awesome site for students and teachers.
CNX: OpenStax CNX, offers pages and books/literature on education topics. All content is downloadable and under the creative commons.
Global Text Project: A collection of digital text books/college level literature.
Open Stax College: Free and Open Source College text books.
Text Book Revolution: If you are a student, link this site to your teacher. It can help save you and your classmates tons of money. Teachers…use free books!
Related: Education Resources.