Boundless Learning has launched an upgraded, public iteration of its software (after a year in beta) and it offers college students free, open versions of textbooks. They describe this big money saver as "textbook replacement."
It will not surprise you that publishers are not happy. Three major publishers sued Boundless in April for abusing the intellectual property its authors have created, copying not the actual content but the structure and form of their books.
The company identifies widely used textbooks in certain fields and then takes the best freely available material it can find. The resulting book is offered as an alternative.
The company is not charging at this point but has $9 million in investor funding. The market for college textbooks is estimated at $4.6 billion a year and has long been a target of student protest over costs. Unfortunately, many students deal with the cost by not buying the textbook and trying to get by by borrowing books from the library and friends (often photocopying large portions of the book).
In the past 5 years, I have written a number of posts about open and free textbooks and the attempts to change textbook publication and sales. There have been other companies, like Flat World, that have opened book access by appealing to colleges and instructors to adopt their reduced cost textbooks. Boundless is direct marketing to students with taglines like "Replace your assigned text for 100% free."