There is a YA series where the font is red or green, depending on the character POV. I don't remember the title, and it may be a really good book, but it hurt my eyes too much. Generally, anything other than black doesn't work. And as I get older, white-white pages make my eyes more tired than creamier white pages...

And there have been a few books where the font didn't work well for me. I like ebooks because I can change font, size, background, etc. It definitely is better in that regard!