According to Executive Director Neeru Khosla CL-12 provides “Free access to high-quality, customizable educational content in multiple modalities suited to multiple student learning styles and levels will allow teachers, students and others to innovate and experiment with new models of learning. CK-12 helps students and teachers alike by enabling rapid customization and experimentation of teaching and learning styles.”
You can log into the site using your Google or Twitter account and once there you have the option of searching for content and creating a digital flexbook or to use a book that another member already created. All of the content is free and once the book is created it can be downloaded in a number of formats, ePub (iPad), PDF (computer), or mobi (kindle). Storing the book on the device would be very useful when the internet is not available or very slow. Go to the site and check out the content.