May I get clarification from other more experienced person out there about the meaning and consequence when your book has the tab "Requires app" on it rather than "Buy".. Does it affect your sales?
A book shows "REQUIRES APP" when "disable from webstore" is ticked. A book that has "requires app" are only available on the app, users from the web cannot read the book unless they have the OkadaBooks app.
This feature also helps protect your book from piracy.
You can reach out to firstname.lastname@example.org if you have more questions.