I have an ISBN to publish my novel. It covers ALL electronic versions. To publish a printed version, I would need another ISBN. I have the choice of applying it to either one. The problem is which electronic version to publish/sell? I see only three: Kindle: The best of the best. Kobo: The others. Google Books: Doesn't even rate. That's sad. There's no other online publishers in the running (unless you publish for free on ZILLIONS of available sites). A whole new world!