I do not get the "experience" difference for text-only, but I definitely see the difference for anything that require fixed-space fonts (code) or images.

I read plenty of books over my phone, though. Never been a problem. Also great being able to read on the bus while standing, which you can't do comfortably on a tablet.

As for paper books, I had to go back to reading a paperbook for something that's not sold in digital form and I found insane how bad the experience is. I like reading on the side and every even (or odd) page is a bad experience depending at which point of the book you are in, with being half-way affecting both sides.

Granted all the books I read are usually thick, so there's that.