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.
If you hold a backlit device closer to your eyes, you will get more eyestrain from looking into a light source. The further you have it away, the more the light will scatter. The closer you keep it, the more light will fall in your eyes.
Yes, resolution does matter, a lot. I had a cheap 800x480 7" reader. Didn't have that much trouble reading on it, but I noticed a huge difference when I switched to my higher resolution Flyer....
And I get eyestrain when I read on my e-ink device, unless I'm in a well-lit area.