The latest release of Firefox, version 39, blocks the use of Adobe's Flash Player by default due to security risks in Flash Player versions 18.104.22.168 or earlier. Adobe has released a patched Flash Player in version 22.214.171.124. The latest version of Adobe Flash Player can be downloaded and installed from Adobe's site at https://get.adobe.com/flashplayer/.
While Nxtbook Media's books are safe, we recommend that you install this update.
Alternatively, you can allow Firefox to use the currently installed version of Flash Player and continue on to your book by following these instructions.
By clicking the link at the bottom of this page, you will be taken to the Nxtbook but will see the following screen:
Click on the "Activate Adobe Flash" link.
And then click the 'Allow and Remember' button to allow your browser access to other Nxtbooks.