[Bookatarian]

The Kindle app will only show downloaded titles on your computer. Do you use Kindle for Mac? If so, you should see all your Amazon titles, both in the cloud and on your Mac, that you purchased via Amazon. You can download each one for a local copy in your "My Kindle Content" folder.

Kindle for Mac will not store titles purchased from non-Amazon vendors. However, you can set up Calibre to import all your "My Kindle Content" files automatically. Next, import all your other purchases to your Calibre library. It may take a little to first consolidate all your titles, but then, moving forward, everything is in one place and it is easy to import new purchases.

Calibre contains all my ebooks, regardless of where they were purchased. I then keep a backup of the Calibre library in case of computer failure.