ReadCube Pro is now available for purchase at http://www.readcube.com which includes many features that have been heavily requested including Cloud Sync and a Watched Folders feature, as well as Early Access to all future features.  ReadCube Pro can be purchased using the checkout available on our website for 5$ a month or 50$ a year.  

The following are the minimum version requirements to successfully purchase ReadCube Pro.  If you are unable to checkout successfully, please try updating to one of these browsers:

Internet Explorer - 10
Firefox - 4
Chrome - 11
Safari - 5.1
Opera - 12.1

For any additional purchasing problems, please contact us at support@readcube.com.