CK-12 is working to establish the development and distribution of quality educational content that can be a core text as well as to provide a flexible context for learning.
FlexBook is an open-content, web-based collaborative e-textbook model. FlexBooks download in the ePub e-book format. Currently there are free FlexBooks available in math, science, technology, and engineering. There are algebra, geometry, and calculus textbooks with teacher support materials. In science, you'll find e-textbooks for biology, chemistry, and physics.
I downloaded the geometry FlexBook. After a quick perusal, it appears to be an adequate base geometry textbook. The images below show how the geometry book renders in several e-book readers on different platforms.
B&N eReader on a MacBook (with highlighting, note, and bookmark)
B&N eReader on a Windows netbook
Adobe Digital Editions on a Windows netbook
Firefox EPUBReader on a Windows netbook
iBooks on iPhone 3GS
You can create and edit your own chapters or even entire FlexBooks.
Watch a CK-12 FlexBooksvideo demo
Register for an interactive webinar "Intro to FlexBooks!"
A non-profit organization, the CK-12 Foundation has an objective of reducing the cost of textbook materials for K-12 both in the US and worldwide.
DISCLOSURE OF MATERIAL CONNECTION: http://cmp.ly/0