Originally Posted by toddos
This is why dpi is so important. Your laptop screen most likely has a resolution around 100dpi (a 1080p 15" screen is only 140-ish dpi). That's way too low resolution to read comfortably on, especially if you're holding it right up to your face. An iPhone 4/4S/5, iPad 3, Galaxy III S, Nexus 7, etc (basically any modern high-end phone or tablet) will have dpis well above twice that of your PC, possibly even three times or more.
Start with a high quality device, add a high quality reader (I like Aldiko on Android), switch to "night mode" (white text on black background), and adjust brightness and font size as needed and you may find LCDs a lot more comfortable to read on.
My wife's iPhone 4, at any brightness setting, is better than backlit devices with lower resolution, but can't hold a candle to my low resolution Kindle DX. And night-mode? No, that is extremely uncomfortable. Sepia works best for me.