This amazes many people, but I read a lot on my iPhone. The free Kindle app means that I can select, buy, and be reading a new book from Amazon in under a minute. Ultra-portable, so I have it with me at all times. I turn down the brightness a bit to prevent straining my eyes. I turn up the font to nearly max size, being over 40 and all. The Stanza reader app allows me to read any PDF, or basically any text format that you can think of on it.
The Kindle and other E-ink devices are supposed to be excellent for this..but the price is prohibitive, given what it is. My personal economics are such that a $260 device needs to be able to do more than display text in black and white. Having said that, owners of the Kindle seem to love them.