I have never used my smartphone to try and read a book, I think most people around me would agree that it would not be a fun experience (most people around me have older smartphones with small screes).
I do own a Kindle, though, but my point is that I think many people don't consider their smartphone a "reading device".
I used to do this a few years ago when I was in London. When you have 5 minutes to wait for the next tube there wasn't much else to do as there was no wifi then :)
I do own a Kindle, though, but my point is that I think many people don't consider their smartphone a "reading device".