I plan to release a book on PDF, at first. That's before I think about a printed version and before I invest in any particular platform.
1) On what devices will PDF not functionally work?
2) On what devices will PDF not work in practical terms?
I am most interested in making it available on many platforms, then I will be interested in offering it in the preferred technologies for certain platforms.
I would later consider a tool like Xamarin for cross-platform development. I will avoid native apps...