title_body: Are there studies on whether reading in landscape or portrait mode is better on smartphone size screen?
upvoted_answer: Some where (I can't find it right now), I read that 72 characters per line was best for reading comprehension. When there was less than this the end of line moving your eye to the begging of the next line slowed you down, and when there was more than this following lines become more difficult, because you have to move your head which makes eye tracking more difficult.
  
  The study did not take into account dyslexia.
  
  So I guess it depends on your font size.