From the Wall Street Journal:

While the notoriously secretive Apple remains mum about its education announcement Thursday at New York’s Guggenheim museum, the company is expected to unveil textbooks optimized for the iPad and that feature ways to interact with the content, as well as partnerships with publishers.McGraw-Hill Cos., Pearson and Houghton Mifflin Harcourt are among the education-publishing companies most likely affected by an Apple textbook announcement. McGraw-Hill has been working with Apple on its announcement since June, a person familiar with the matter said.