1. No, print editions and ebook editions can never share an isbn. (Ebooks not always properly edited on copyright page to reflect). Absolutely not allowed by isbn agency under any circumstance.2. If only readable on a specific device, unique isbn or bookseller identifier needed.3. If only selling directly from author site or their publisher/distributor, isbn not required (and no worries if odd isbn information displayed). Bookseller sites and stores need. That includes sites like Smashwords and Baen allowing multiple types of files to download but only using one ebook isbn. Still not allowed to use ebook isbn for print book and vice versa; but okay if the one author or publisher site not setting a new isbn for direct download files.
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