We have had users who complained that contents were incomplete, because the reader Menu bar was blocking some content. Tapping on your screen when a book is open hides the Menu Bars and make the entire book content visible

Tap screen to hide bar

Scrolling is dependent on device. By default some scroll from left to right, others from up to down. Therefore ensure you try the left and right scroll or up and down scroll. One of which must work for your device