You can use the previous page and next page buttons if you have more e-books than can fit on a single screen. (davidderrico.com)
The least you could do is put some kind of Next page button at the bottom, I had to scroll up and change after every page. (timeout.com)
The Previous Page button runs down two - thirds of the screen on the left side, while a second Next Page button takes up the lower third. (macworld.com)