I was originally going to take credit to this myself but I have to hand it to my sister who actually discovered this while using the Geometry textbook which I personally loaded for her!
It's a sub-menu accessed by double clicking on the right side of the screen. I'll go through the steps below with pictures:
Open to a page in a PDF (I've checked with the books in FB2 they loaded and it works there too, if anyone else has any other formats let me know):
Lightly double tap on the right side of the screen and this menu pops up!:
Now, the bold number at the bottom represents what page you're on. You can jump to any of those numbers by clicking on them (they range 4 numbers before and 4 numbers after the page you're on) or you can use the "+10" and "-10" buttons to add to the list of pages to jump to.
Above that are pages that you've already visited - i jumped around so as you can see my recent page visits are jumbled in numbers.
Now there are 3 pictures at the top right, in descending order i'll describe them below:
The 1st one (and the coolest) is the Table of Contents:
It breaks down chapters with chapter titles so you can jump from one to another. Pretty convenient when a teacher might say "Now class, go to chapter 4."
The 2nd one is bookmarks. Now i only bookmarked one page to show the function, but you can probably do this to however many pages you like. What's interesting is that a virtual keyboard popped up and let me title the bookmark itself. Since the page was about line segments, i titled it "Line Segment." (When i did this in FB2, it gave me the page number followed by the first words on that page), and this is how the lonely 1 bookmark looks:
The 3rd function is a "Page Jump" feature where a block of numbers pops up on the screen and you input what page you want to jump to:
If anyone else finds anything make sure to post! There's not a lot of info on the functionality of the device yet so i'm interested in seeing what other features they've locked up in here