It appears that Apple plans to include support for iBooks Textbooks on the iPhone and the iPod touch with the launch of iOS 7



From MacRumors:

As noted by 9to5Mac, the iOS 7 App Store includes a new "iBooks Textbooks" section in the educational category. The section is currently unpopulated, but it does contain the framework for future textbook offerings. There are a number of subject headings, including Humanities, Life Sciences, and Physical Sciences, which include promotional graphics optimized for the iPhone. Section headings are also populated, advertising a number of book bundles like "High School Core Curriculum" and "School Yourself Hands-on Calculus."

  iOS 7 May Include iPhone Support for iBooks Textbooks