As a student in a school just beginning its iPad program (so far 2 years), I have tried many different textbook viewing apps, including Kindle, iBooks, Kno Textbooks (renamed Intel Study), and Pearson eText. After only a few months using this app I can already tell it is one of the best to use. I love how you can purchase individual apps, and the User Interface is easy to navigate.
Ndjdjchfkdjvkd about eBooks by Inkling, v3.9.4