The Myth of the eISBN: Why Every eBook Edition Needs a Unique Number | SELLBOX.
Some publishers these days are referring to eISBNs – as if they are separate from the regular ISBNs. There is no such thing. An ISBN is an ISBN. You need a different one for each format you publish in: hardback, paperback, .ePUB, .Mobi and .pdf.
But there is no eISBN. Just get your 10 ISBN’s and use one for each format. Simple.
Stop confusing us newbies!!!