This paper describes experiments investigating factors that contribute to the readability of computer displays. We present two experiments that focus on reading text from various display technologies, ranging from paper to novel, high-resolution, flat panel displays. This work represents a sequence of controlled experiments and field studies aimed at better understanding the affordances of paper and corresponding design requirements for portable reading devices. Our efforts update previous studies and consider new factors afforded by advances in display technology. Although our findings indicate no statistically significant performance differences between reading from paper and reading from electronic displays for intensive, short proofreading tasks, users nonetheless indicate a strong subjective preference for paper. Evidence from a second experiment indicate that the previously unexamined factors of weight, flexibility and thickness are significant factors behind this.