Each marketplace has it's own Rules. Imagine renting space from different landlords in the Town Square to sell your books. In one, you have to purchase a special ISBN peculiar to them and no other Space. (NookPress). It costs $10 per number from Bowker. In another, there's $54 Hello Money (Ingramspark) for print and digital and your print edition isn't working cos they keep telling you you've formatted it wrong, or the metadata doesn't match, and when you ask them why, and what can be done, there's silence for several days followed by a cryptic response that makes no sense. On Ingramspark, I have to get software to convert my .docx to .epub. And - the interface hasn't got a Friendly look, though it assures you that they welcome the self-publisher. I've no doubt if you know your way around it, it's ok, but the support is slow. And what is Lightening Source anyway?
Over at Amazon, the landlord tells you that he's moving you from the Space you have occupied for some time to another, and you have to set up all over again. Actually, he has moved the books for you already, from CreateSpace to Kindle Direct Publishing. He's helpful, but tells you that you have to redesign your paperback covers - no matter - you can do it right there with their software. OK. the new Cover Creator is a bit limited, but then you can upload your own print-ready PDF. Fair enough.
Now here I am running between three Spaces. There are no sales from Nook or Ingramspark, but Amazon KDP is seeing some, and getting very good Reviews...I think about enrolling in KDP Select to reach a wider audience, but must first take my digital edition off sale in the others.
Which leads me to think that it would be far less complicated to vacate Ingramspark and Nook since there's no movement there anyway so I decide to at least take my digital edition off-sale in Ingramspark - but there is no way for me to do that on my end. That's a bit annoying. Nook Press - no problem, I can do it. Done in three clicks.
Three days after asking Ingramspark to take my Title off sale (in fact, I decided to end the relationship completely, though I'm down $54) they do it. (I'm a little offended they didn't even try to keep me, but I have zero sales and they have their Hello Money).
I now have digital edition exclusivity with Amazon.com, and all my Titles are in KDP Select.
It means I can also delete all the How-to and Guides related to Ingram Spark and Nook on my hard drive. Declutter that!
Now, let's think about Amazon Ad Campaigns.