I'm talking about my phone's kindle app, not an actual kindle. You have multiple settings with a kindle app, white on black, black on white (like a real kindle) or some weird sepia toned thing, and continuous brightness settings; night reading using white letters on black background uses a ridiculously small amount of battery power, even so with daytime reading at higher brightness. Black letters on white uses a lot more energy. You also have numerous font sizes, and the screen auto-rotates portrait/landscape. Easy to hold in one hand and swipe pages with your thumb.
I have the kindle paperwhite, basically gave it to my wife because I prefer the kindle app over it even at home. Try it sometime (the Kindle app).