Short version: If you send a third-party mobi book to your kindle, it will sync between Kindle apps, but only if they are on a Kindle, iOS or Android device the cloud reader and PC applications (maybe Mac, too?) will not have the book or its associated notes/highlights.

I then went to my iPad (without sending the book there explicitly) and it was there with my highlights again. I picked my iPhone, and sure enough the book appeared there with my highlights (yay!). This brought up a window with a drop-down list of all my devices - except my Kindle for PC or the Amazon Cloud Reader were greyed out. I then clicked on the action button next to my book and clicked the Deliver to: Others link. The Kindle application lets you not only manage. Locate the folder with Kindle books on your computer. Download the books from the cloud to the app. The book did not appear under books, but DID appear under Docs. There are four steps to back up Kindle books via Kindle desktop app: Download the Kindle desktop application (there are versions for PC and Mac). I called Amazon support and here's what we learned: we went to Manage Your Content and Devices and clicked on YOur Content. I started to worry at this point, thinking that I only ever have access to my highlights on the Kindle device itself. I also checked my history of highlights at and they were not there either. However, I discovered that the book did not appear on my Kindle for PC. I made many highlights (as I often do), and I wanted to see those highlights on my PC to prepare some teaching notes.

It was delivered to my device right away, and I happily read it. I used the Send to Kindle application on my PC to send it to my Kindle device (strangely, by Kindle for PC was not on the list of options - more on this later).

I purchased an ebook in Mobi format from a seller other than Amazon.

Kindle app for mac desktop