It's not an app. It's a proposed API. It has lots of potential I agree. But nothing downloadable yet unfortunately. It's meant for developers right now to incorporate into their apps. To my knowledge, no app has launched with it. Not on iOS anyways.
Sadly, as an educator, I am not big on reading books as I just can't find the time. I find myself reading more informational texts from sources such as NGM and The Week Magazine (Flipboard on my iPad is my friend for this reason). HOWEVER, I would really like to see how this works for reading a book. I might actually start reading more biographies and such.