In my opinion, the realize reader (specifically I'm thinking about the TEs for the Integrated math curriculum) should stop trying to simulate a physical book, since it exists in a digital medium.
If we could navigate the textbook more like a pdf by scrolling instead of waiting for it to turn pages, I think it would be much faster to navigate. In its current state, navigation is clunky because on some screens you can't even fit one page of the book and the only options for scale are 0.5x and 1x. Then to navigate to the next page you have to click and wait for the next pages to load. I picture being able to scroll through the book in its entirety, or at least an entire lesson or topic if that would cause backend issues. You could also put an index toolbar on one of the sides so you could jump around the book faster.