= an openly-licensed textbook offered online by its author(s). The open license sets open textbooks apart from traditional textbooks by allowing users to read online, download, or print the book at no cost.
From the Wikipedia :
"An open textbook is an openly-licensed textbook offered online by its author(s). The open license sets open textbooks apart from traditional textbooks by allowing users to read online, download, or print the book at no cost.
Open textbooks are increasingly seen as a potential solution to some of the challenges with the traditional textbook publishing. model.
For a textbook to be considered open, it must be licensed in a way that grants a baseline set of rights to users that are less restrictive than its standard copyright. A license or list of permissions must be clearly stated by the author.
Generally, the minimum baseline rights allow users at least the following:
- to use the textbook without compensating the author
- to copy the textbook, with appropriate credit to the author
- to distribute the textbook non-commercially
- to shift the textbook into another format (such as digital or print)
Many authors also grant rights such as:
- to add, remove or alter content in the textbook, often on the condition that derivative works must have the same license
- to copy and distribute the textbook without giving credit to the author
- to use the textbook commercially
Some advocates believe that the baseline rights must be more extensive to be considered "open". (http://en.wikipedia.org/wiki/Open_textbook)
From a testimony for the U.S. Congress by David Wiley, a good introduction to the topic of Open Textbooks:
"Affordability. Part of the rising cost of higher education for students is the ever-increasing cost of textbooks - textbooks can add as much as $1000 per year to the cost of college. The National Association of College Bookstores says prices of college textbooks have risen nearly 40 percent in the past five years. In a survey of textbooks by the California Student Public Interest Research Group, new editions of textbooks cost 58 percent more than previous versions, with an average cost of over $100 per book. (Crane, 2004; Pressler, 2004). The impact of these costs is especially severe on low-income students. According to the General Accounting Office, the costs of textbooks represents 26 percent of the cost of tuition and fees at public four year schools, and almost a full three quarters of the cost of tuition and fees at 2 year public schools where low-income students are more likely to enroll (Bershears, 2005).
Frankly, the textbook situation is wreaking havoc on teaching and learning practices on our campuses, with as many as 43 percent of students foregoing the purchase of required textbooks due to financial considerations (Crane, 2004). When less than three in five students in a class have the materials they need to support their learning, there must be an acute impact on educational effectiveness.
While efforts like the OpenCourseWares are making great strides in providing curriculum materials in an open way, the development of open textbooks that could be voluntarily adopted by university faculty has been very slow to occur." (http://opencontent.org/blog/archives/249)
- Potto Project - Open Engineering Textbooks
- Open Text Book is a registry of textbooks (and related materials) which are open — that is free for anyone to use, reuse and redistribute 
Our entry on Open Access E-Textbooks list suppliers as well:
- Flat World Knowledge
- Community College Open Textbook Collaborative
- Free Digital Textbook Initiative 
- OER Commons
- An open textbook initiative by Economics Professor David Levine at http://levine.sscnet.ucla.edu/general/intellectual/open.htm
DRM a major barrier to e-textbook adoption
"A study published this month by a coalition of student public interest research groups (PIRGs) has identified key problems with e-textbooks, and it calls for schools and publishers to adopt open content licenses, such as those offered by Creative Commons.
The report explains that the high cost of textbooks represents a significant financial burden for many students. Although digital textbooks have the potential to mitigate this problem, a survey conducted by the student PIRGs found that e-textbook services offered by mainstream publishing companies fail to provide a compelling alternative to conventional print books.
According to the study, a majority of electronic textbooks are encumbered with DRM that limits printing to 10 pages per session and imposes a 180-day expiration period. Despite the restrictions, the electronic textbooks don't cost significantly less than physical textbooks. In fact, the study found that the total cost is roughly the same in cases where students sell textbooks back to the school bookstore at the end of a semester.
Individual students spend between $700 and $1,000 annually on textbooks, the study says. Textbook prices continue to escalate and have already increased by over 300 percent in the last 20 years. Traditional market forces aren't bringing the prices down because students are a captive audience; professors pick books but don't buy them, and students have no choice of titles for classes. To reverse this trend, the student PIRGs advocate adoption of open textbooks that can be distributed free on the Internet under open content licenses." (http://arstechnica.com/news.ars/post/20080828-study-students-need-open-source-e-textbooks.html)
Issues with Open Textbooks
P. Smythe: 
One of the greatest concerns about open source textbooks amongst teachers, administrators and the greater community is the the issue of quality control (Harley et al. 2010, De Koenigsberg 2010). Truly opening access to authorship leads to the situation where ‘anyone can contribute anything’ (Baraniuk 2006). Though this has huge potential, it also raises the issue of quality assurance. In my opinion, how well this issue is dealt with will ultimately define the success of the movement, and whether the move to open source is viewed as a economic imperative, or a truly pedagogical imperative.
Various platforms use different quality assurance mechanisms (Frith 2009) usually limited to the following (or some combination thereof) ; reputation and endorsement; centralised peer review; and user review (Hylén 2006). The most successful platforms such as Connexions use a combination of approaches which assure high quality resources without compromising the open ideology (Connexions 2007, Frith 2009).
Further to their role as quality assurance mechanisms, aspects such as authorial attribution and user feedback have positve effects in other realms. Authorial attribution acts as a strong motivation for creating content (Stewart 2009, Seidel 2009) perhaps to offset the diminished financial gain from publication. I believe that user feedback has the potential to become much more than a QA measure as teachers are able to share ideas on how they used a resource effectively. In this sense, such a system would provide another powerful community based tool for knowledge sharing (in this case, pedagogical).
A common perception of the open source movement, is that it will lead to the reduction, or removal, of price-barriers to knowledge and may close the knowledge divide (Kurshan 2007), gaps between access to quality education of different groups in society. Despite the successes in closing the traditional digital divide (access to computer hardware), a new digital divide is opening for a small minority, in terms of their ability to access knowledge (Green & Hannon 2007) . With respect to open textbooks, the issue of access to computers and high-speed Internet in the home are crucial when considering a truer picture of access to knowledge. In California, where an open textbook project is currently being rolled out, there are real fears that poor students will be at a disadvantage (Lewin 2009) in the move to open textbooks.
This problem can be alleviated to some extent as the move towards one-to-one computing is actualised. In Australia for example, the federal government has committed to having a one-to-one student-to-computer ratio by the end of 2011 (Gillard 2008, Rudd 2009). In my opinion, Australia would provide near-ideal conditions for trialling open source texts as students should not be limited by access to hardware (though others have made the link between one-to-one computing and open source textbooks (Platoni 2009)). Further, the realisation of the national curriculum will bring about a necessity for publishers to revise existing textbooks, and has created a genuine opportunity for change in current curriculum implementation and pedagogy.
Other issues in relation to the digital divide go beyond that of our western perspective. The ability of open textbooks to provide quality content to the developing world has been lauded (Foster 2008). Open licensing allows texts to be freely translated, or for examples to be edited to include culturally relevant material (Baraniuk 2006). Though this appears to be a great solution, it is difficult to gauge the impact, and scale of this movement. The appearance and growth of a number of open text platforms specifically for the developing world (for example, Free High School Science Texts n.d.) is simultaneously encouraging and disturbing. Access to knowledge in the developing world is increasing, however the existence of specific platforms to serve only the developing world may create a two-tier system, perpetuating inequity in access to knowledge.
Implications for educators
Beyond the social dimension, there are some huge implications for educators. Moving to open textbooks whilst maintaining the dominant teacher-centric model will have little effect on digital literacy, and represents a missed opportunity (Geser 2007). Arguably the greatest value in the open textbook movement is that it signals a move away from traditional textbooks, creating an opportunity for highly interactive and customisable education resources which promote a collaborative and creative approach to learning (Geser 2007, Kenney 2009, Frith 2009). Further, the complete open access to authorship in some platforms allow for a constructivist approach to learning (Frith 2009) and a democratic approach to curriculum as students can engage in course design and the construction and editing of textbook materials." (http://psmytheteach.wordpress.com/2010/03/11/research-summary-1-open-source-textbooks/)
The role of Apple in creating a new marketplace
"Apple's ibooks 2 application
Apple continues to transform education, now taking aim at the broken educational textbook industry. The creation, publishing, approval process, and distribution of educational textbooks for elementary, secondary, and university education have been ripe for a customer revolution for over 20 years. On-demand printing and the Internet both helped to accelerate the process. Visionary undertakings like Nature Education’s Scitable offering (high quality free life sciences’ learning materials) have also helped to pave the way. But it took Steve Jobs’ vision of transforming educational publishing to make this a reality.
What Apple has done is 1) to make it easy for students and teachers to access high-quality interactive learning materials for free from Apple U (via iTunes), 2) to provide tools (ibooks author) that will make it easy for more people to create and to publish high-quality, interactive educational content and 3) to provide a win/win business model that keeps educational publishers in the game by letting them sell electronic textbooks at lower price points (e.g., $14.99) to a much larger number of students worldwide." (http://outsideinnovation.blogs.com/pseybold/2012/01/apple-to-transform-textbook-publishing.html)
Summer 2010, NYT:
"progress with these open-source texts has been slow.
California and Texas dominate the market for textbooks used in kindergarten through high school, and publishers do all they can to meet these states’ requirements and lock in their millions of students for years.
Both states have only recently established procedures that will let open-source textbooks begin making their way through the arduous approval process. Last year, Texas passed a law promoting the use of open, digital texts and is reviewing material that might be used in schools.
In California, a state board is studying whether open texts meet state requirements. The CK-12 Foundation, a nonprofit financed by another Sun co-founder, Vinod Khosla, has created several texts that have met the board’s criteria.
“In three and a half years, we have developed nine of the core textbooks for high school,” says Neeru Khosla, Mr. Khosla’s wife and the head of CK-12. “If you don’t try this, nothing will change.” (http://www.nytimes.com/2010/08/01/technology/01ping.html)
- See our entry on Open Content
- An open textbook initiative by Economics Professor David Levine at http://levine.sscnet.ucla.edu/general/intellectual/open.htm
- The Open Textbook Initiative, at http://wiki.bssd.org/index.php/Open_Content_Textbooks
- Richard Baraniuk of Connexions on Open Source Learning and Textbooks ; Richard Baraniuk on Open Textbooks and Open Educational Resources
- Social bookmarking via Friendfeed room at http://friendfeed.com/rooms/opentextbooks
- Special issue of Educause: The Case of the textbook: Open or Closed? 
- Find Open Textbooks: search engine
- Paper: A sustainable future for open textbooks? The Flat World Knowledge story. by John Levi Hilton III and David A. Wiley. First Monday, Volume 15, Number 8 - 2 August 2010