Lots of great suggestions above! Here's mine:
* Let us
CHANGE the
INTER-LINE SPACING. So the sentences can be closer together, thus requiring fewer page turns
* Let me
ROTATE the book 90 degrees to the
RIGHT. the buttons are then left had accessible, wider is sometimes better than narrow (landscape vs. portrait reading in other words).
*
READ while
CHARGING. 'enuf said.
* glow in the dark!!!! (ok, i'm being silly)!!
*
And for KOBO II??? chuck a couple solar cells onto the front and let it self charge! WooHoo!