"Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution 3.0 License. This seems to be a good choice. Many "open" textbook projects (e.g. this one from Florida) attach "Noncommercial" or "No Derivatives" clauses, which limit downstream re-use and adaptability.
Some additional reading on the generally poorly understood noncommercial clause:
Lists of free textbooks (or similar)
Note that lists of "free textbooks" may not always mean "free-as-in-freedom" (so caveat lector!).
Other stuff (to add)
Kno Textbooks provide a catalogue of 200,000 electronic textbooks for K-12 and HE from 65 major publishers including Cengage, Houghton Mifflin Harcourt, and McGraw-Hill for iPad, Android and Windows 7. They're not free - but might be of interest ... Could also mention wikiversity and wikibooks (wikipedia sister projects)
The advantages of ETextbooks
Particularly where ETextbooks are made from blocks of OER there are a number of key advantages to ETextbooks over traditional books, including:
- easy updates,
- "wear and tear" issues gone,
- ability to highlight and save for later snippets,
- can embed interactive content (multimedia such as videos, and quizzes or longer assignment submissions)
- can be customised to individual schools or/and students/teachers, etc.
- ETextbooks can be searched
- Where ETextbooks are not openly licensed, the market for second hand and older editions of books is removed, potentially removing access for some