I put about 500 books on mine today and started browsing a bit. The books were all in weird sequences even though they were supposedly sorted alphabetically. Then I remembered seeing a setting about organizing books by series and I went into settings and turned that off. Now they're organized just like I would expect.
I did experiment a bit with the button, switching which button does what. I found I like the bottom button going forward better but not by much. But I've all but stopped using the buttons. I'm used to swiping. Buttons are for old people.
Barry