There sometimes are problems with the Play Store when it comes to downloading, installing, or updating apps.
One common fix is to clear data and cache for the Play Store and Download Manager apps. You can access these app settings through the Settings Menu on your device, and then Apps or App Manager. For each app, tap Clear Cache and Clear Data. Once you've done this, restart your device and try downloading the game again.
If that doesn't help, please reference the steps on this page to see if that helps:
http://support.google.com/googleplay/android-developer/answer/1067233