"There's an App for that!"
There are many apps that are available for reading e-books. Most feature a library of classic books. In addition the apps have the ability to change the size of the font. The Narrator app is the one application that I have found that will also read the text while highlighting. Currently three books are available (Call of the Wild, Anne of Green Gables, and The Tale of Peter Rabbit) with more promised by the creator.
I have also made use of the free Kindle app. This app allows you to purchase books through your Amazon Kindle account and have them available on your iTouch or iPhone. Surprisingly I found that reading a book on the iTouch was pleasurable and did not cause me any eye strain--and I have old eyes. Now I have a book available wherever I am: waiting in the doctor's office, waiting for my children, or while traveling.