Saw this is the Featured Apps and Games section of the Amazon App, was $4.99.
I saw there's a promo of the iOS version, maybe it's coming to the Android version but it's currently A$6.53 in Google Play Store.
Looks like it's the first episode, with subsequent episodes as in-app purchases. As usual with the Amazon App Store, I see a few complaints about slow updates. But hey it's free!