Flat World Knowledge offers free access to digital textbooks online . The company charges $ 20 for downloadable PDF-format books . Interest in the company is rising ; the service will be at 400 colleges this year . Comment:
Flat World Knowledge offers free access to digital textbooks online . The company charges $ 20 for downloadable PDF-format books . Interest in the company is rising ; the service will be at 400 colleges this year . Still , the digital textbook business remains in its infancy , author says .