Free PDF Textbooks Sources

Google PDF Search: Google's indexing robots do a terrific job of finding PDF textbooks. Search using this format: filetype:pdf "textbook title"
Openstax: The Bill and Melissa Gates Foundation and others have funded this open textbook project.
Google eBook Search: a custom Google search engine for just ebooks
College Open Textbooks: a collection of twenty-nine educational non-profit and for-profit organizations, affiliated with more than 200 colleges.
Digital book index: links to more then 150,000+ digital books from various universities and publishers. Around 100,000+ of these books are available for free.
Project Gutenberg: the oldest digital library in the world offers more than 43,000 e-books, completely gratis.
University of Pennsylvania: a mini-site which links to free textbooks available on the internet. It has over 1 million free eBooks. They keep updating the list regularly.
Reddit Tracker: Tracker for PDF and eBook of college textbooks and free sources
Boundless:They use public sources to compile information and align it after the big selling college textbooks. Not the same publication but the similar content.
Flat world knowledge: offers free and open college textbooks. They have textbooks from well-known authors and scholars in their catalogue. These textbooks can be read online using their easy to use online reader.
Book Boon: A lot of free college textbooks in PDF format.
Open Textbooks Library: 1,000+ Open Textbooks and Learning Resources for All Subjects

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