[nico]

Be aware that the new version of the Kindle book (including the new cover) will NOT be available to people who have already purchased it. In order to make that happen, you have to contact KDP and have them issue an update. I can give more details, if you're interested.

 

[nico]

You need to use the Contact Us form on the KDP help website. Contact KDP and tell them the details of the changes you've made to your book (in this case, cover). They will evaluate how "serious" the changes are and eventually enable changes on the My Kindle page of their website. This can take several weeks. And the readers will have to know to update it manually. It's a little frustrating, but better than nothing.