KML is the extension used for Hiebook eBook files. However, the extension is also in use by Google maps to identify a format for storing Waypoints and Tracklog. When used by Google it stands for Keyhole Markup Language.
 Source Format
 Creating KML
EBooks in the format are still available commercially and can be made by users with the following programs.
 Viewing KML
In addition to the reader there is a Windows program included with the device that can read KML files.