I just desire to BE reading. I don't care how fast or slow I consume. Too many different factors (mood, time of day, alertness, external stimuli, interest, writing style) contribute to my reading rate at any given moment to attribute all that much extra weight to margins, or characters per line, or line-height, or screen technology and such.
I gave up focusing on how well, or how fast, or for how long of a stretch I read. When I want to read for a long period of time, I read for a long period of time—regardless of typographic minutiae or screen technology. When I don't feel as motivated to do so, then I read in shorter spurts. I've always been fickle in this regard. Even when paper books were my only choice.
I like to read. Analyzing how (or how well/fast) I read?? Not so much. Reading is the goal for me, not
finishing. *shrug*
NOTE: post not intended to diminish the topic, nor to seek to belittle/end the discussion. By all means, carry on. Just my opinion.