Here in Virginia each county and city selects its own texts from an approved list. There is always a great debate over the science and math text books (even more so than the debates about the history and English texts.) For the science texts the creation issue is still alive and hotly debated. In the math area there is the constant battle over methods of instruction -- math, new math, new-new math, etc. The last reason given for a change in the elementary school math books was that the word problems were out of touch with the current world -- "A train leaves Boston ...." Many were also considered to be sexist and stereotyping.
I think the first major area for most US schools will be in the English and lit classes as many (if not most) of the required reading lists are already available in gutenberg and manybooks.
The cost of textbooks is skyhigh due to the "limited" distribution they have. Etexts answer this problem. I have heard of a school system that requires high school students to leave THE textbook in the desk as all classes must share the same book since there is not enough money to buy a copy for all of the students taking the course.
I remember in college that the cost of the textbooks was more than I paid the school to take the courses.