Because Book Creator for iPad has been around since 2011, we've seen examples of some students taking advantage of the amazing advanced accessibility features of an iPad to interact with books in ways we wouldn't have thought possible.
If you're interested in switch controls for iPad, you should read Apple's support article: Use Switch Control to navigate your iPhone, iPad, or iPod touch. It details how to set up and manipulate a switch.
There is a great example included in Rosey McQuillan's book on differentiated learning. The student uses two switches - one to read the book and another to turn the pages.
Video courtesy of Wendy Buckley, an Assistive Technology Specialist at Perkins School for the Blind, Massachusetts, USA.