"I don't like reading off a computer screen" — it's a cliché of the e-book world. It means "I don't read novels off of computer screens" (or phones, or PDAs, or dedicated e-book readers), and often as not the person who says it is someone who, in fact, spends every hour that Cthulhu sends reading off a computer screen. It's like watching someone shovel Mars Bars into his gob while telling you how much he hates chocolate.
But I know what you mean. You don't like reading long-form works off of a computer screen. I understand perfectly — in the ten minutes since I typed the first word in the paragraph above, I've checked my mail, deleted two spams, checked an image-sharing community I like, downloaded a YouTube clip of Stephen Colbert complaining about the iPhone (pausing my MP3 player first), cleared out my RSS reader, and then returned to write this paragraph.