Hailey has discovered the Diary of a Wimpy Kid books and is devouring them as fast as she did the graphic novels. She said the letters don't jump around on the pages and it's interesting and fun to read. I think the fact that the letters are of a darker and larger font on slightly yellowed paper makes a big difference for her visual processing.
(The Diary of a Wimpy Kid books by Jeff Kinney are in the fifth grade reading level range. So the fact that she is a sixth grader reading them fluently - yes she is reading them at a fluent speed and not slightly slower - is wonderful!)
UPDATE: I was told the Kindle Fire enables you to change the font size and color of the text as well as the background "paper" color. I want to find out more about people's results with using this feature, especially if you have a visual processing disorder or dyslexia. So if you can tell me anything that might help, I'm ready to listen!