CK12.org FlexBooks - Very Cool!

I stumbled on this while looking through Amazon's list of free e-books for Kindle. I've gotten some really amazing free books since I started using the Kindle apps on my iPod Touch and PC, so I sometimes check. Many of the free ones are public domain books, classics and others, but sometimes you find recent books that publishers are giving away to promote an author or a series (this is how I discovered Naomi Novik's great "Napoleonic Wars with dragons" Temeraire series).

This time I found some interesting free science textbooks from something called ck12.org. I downloaded several (earth science, "people's physics," nanotechnology, calculus, biology) and started reading one on "21st century physics" that is really interesting and well written*, with a sort of dialog format on subjects including gravitation, nuclear energy, particle physics, biophysics (medical imaging), etc. This is apparently intended to supplement basic physics topics found in standard textbooks with updated material on diverse, interesting topics and many web links. But who is offering this? I found this on the web site:

CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the "FlexBook," CK-12 intends to pioneer the generation and distribution of high quality educational content that will serve both as core text as well as provide an adaptive environment for learning.

Cool. I also watched a video and found that these FlexBooks can be viewed in various formats, printed, and even customized by teachers! Wow. This is good. I will learn more.

* the "well written" part varies by topic, with each chapter of this book written by a different author. I just read a chapter on on nanoscience that has several serious errors that completely change the meaning of some sentences.  Textbooks need editors, even if they are free electronic textbooks.