Nothing beats an e-ink reader for outside reading whereas the Ipad emits light and thus it is cancelled out by sunlight and of course the glare issue. Although I did not notice it as too striking on my Ipad Mini but of course I don't read much outside.
One thing you could try is reversing the colors so the background of your Ipad would be black and the words would be white. I am just saying that off the top of my head but it could render the Ipad readable in daylight. Oh and Marvin can do that in the options
