Apple and Amazon have gone to far with their controlling users. Plus the service even works on the Kindle smartphone app. If you search for a book title it will tell you in the full description if Whispersync for Voice is available and the upgrade price. I cannot afford to buy a new mac let along pay for upgrading all my apps just to run on 10.10 on my 4yr old iMac. Are all Kindle books available on Whispersync No, not all but there are over 30,000 titles currently available with more being added on a daily basis. Would you trust Apple and Amazon now? I live on SSI/SNAP due to disabilities am born with. So content I have in my Amazon account is forever locked up out of my use until I upgrade my Os and the Kindle app. And on sep.15th the app on my iMac will no longer work at all anymore. Amazon has over 15,000 Kindle books available with Whispersync for Voice. Now the feature has been expanded to include Audible audiobooks. Senior Amazon support staff explained that Apple requested Amazon force all Mac kindle users to upgrade to the 10.10 before they can use the latest Kindle app. Whispersync was formerly just for Kindle books, you could start reading a Kindle book on your Kindle, pick up your iPhone and continue reading on your Kindle app where you left off reading on your Kindle. You can check the Kindle version number by choosing 'Kindle' from the menu of your app and then selecting 'About Kindle.' Please see our troubleshooting pages for Kindle for Mac if you have any other questions. You can easily download and install the latest version of the Kindle for Mac from our download page on Amazon. Our latest update (version 1.11.0 or above) is still free, and includes important bug fixes that are required to continue using the app. It's time to update your Kindle for Mac app! We appreciate the time you've spent reading with our Kindle for Mac app, but you have registered a version on one of your computers that is out of date and scheduled to be retired by September 15.

Would like to share an email I got from Amazon a few days ago:

How to add whispersync to kindle book