for future reference - presently you can move your Kindle between accounts at will. Ownership of the books belongs to the account, not the Kindle. But any books that you have ON a kindle will remain there when you de-register the device unless you manually remove them.
On your Manage My Kindle page, if you have zero Kindles/Apps/Kindle for Mac etc registered then your list of Kindle books will disappear. But they return once you re-register a Kindle to that account.
And again, welcome to MobileRead
