Re: Format of choice for immediate offline reading, easy sharing or simple portability
>giant screens< - 25 years ago 1024x768 on a 14" VDU was normal, more than a couple of pages of PDF filled the spare RAM space on an average computer, (queue renditions of "when I was t' lad...") and if you had said people would volunteer to use 5" screens, people would have died laughing.
ePub&HTML may well be better for the current phones but after 25 years PDF is now the defacto minimum standard for documents in a graphic format, it'll still be here in another 25 years just like .TXT