You will also find the left and right-arrow buttons useful when moving to a specific chapter in a long book... if there are more chapters in the TOC than can be displayed on one page, rather than having to scroll all the way to the bottom to force the next page of chapter shortcuts to display, just use the right-arrow.
In addition, if you are busy reading the book and fumble the next page button, you may see the screen grey out and freeze with an underscore and a number after it in the middle of the screen. This just means you have accidentally tried to navigate to a specific page number. Normally, you would press, say, 5, 6, 0 then the central circle in the right scroll ring to go straight to page 560. If you do this by mistake, just press the menu button to clear it and return to your page.