If you don’t do this, Kindle for Mac will automatically update to the latest version which doesn’t work on Leopard. Alternatively, a better way to go is to use Kindle on OS X 10.5.8 is to use Kindle Cloud Reader which is Amazon’s online version of Kindle.

Earlier this year Amazon updated their Kindle for PC and Mac programs to add more accessibility features and support for enhanced formatting.

In order to add the new features, they changed the format the programs support from AZW to KFX.

This behind-the-scenes change doesn’t mean anything for most people, but for those that prefer to remove DRM from Kindle ebooks, then getting KFX ebooks is a big problem.

There’s currently no way to remove DRM from KFX ebooks, so Calibre can’t convert ebooks that are in KFX format (although it can convert to KFX for the added features), but there are ways to get AZW ebooks instead.

The change started with version 1.19, so you can still download and install an older version of Kindle for Mac or PC. In fact Amazon still hosts the files if you know where to find them:

Kindle for PC 1.17 (links no longer active)
Kindle for Mac 1.17

First thing, make sure to go to Tools > Options and turn off automatic updates!

Kindle Reader On Mac

Download Kindle Cloud Reader For Mac

Another way to get AZW files instead of KFX is to use the “Download & transfer via USB” option from the Manage Your Content and Device page at Amazon, but this only works if you have an E Ink Kindle registered to your account.

Amazon Kindle Reader Download

There’s also a way to get the newer versions of Kindle for PC and Mac to download AZW files instead of KFX. It works with versions 1.19 and 1.20. See Method 2 on this post at MobileRead for detailed directions. All you have to do is copy and paste a line of code into the command/terminal window to block the program from using KFX files so it will download AZW instead.