A Textbook "Open" and Shut Case

As a professor, I am keenly aware of the high cost of textbooks that I require of students. Over the years I have stopped using textbooks for some upper level courses, but they are still a necessity for many courses.
Yesterday I received an email from the Student PIRGs and the Make Textbooks Affordable campaign about Open Textbooks. I had been thinking about starting something along the same lines, so I was glad to see someone take the lead. The idea is to promote Open Textbooks, which can be used free of cost in a digital form, or at a low cost in printed form.
It is time I started writing my own textbook....

Make Textbooks Affordable