I would develop the app using Xamarin to lower the cost and make it easier to maintain.
A little back-end could be done using Parse or Azure, so relevant data could be updated without releasing a new version of the app (like the links for buying the books), same provider could be use for push notifications.
The eBook feature might be a little unnecessary, because:
-there are already a lot of great apps to read books
-users like to use those apps, they are familiar to them, and even if we create an awesome eBook reader, some people simply wont like it, and would be frustrated to not been able to read a book using some other app.
-it would probably take a lot of time (and money), not only for the current development, but for future update and fixes due to unexpected bugs, os updates, etc.