Field Guide to Butterflies App for Android FREE Today Only

Today only, Amazon is offering a FREE download of the Audubon Field Guide to North American Butterflies app for Android. I understand it's also available for the Kindle Fire. This app includes 2,000 photographs and 600 descriptions of butterfly species living in North America. This is not an endorsement on my part, as I've never used the app myself, but since it's free, it's really a "can't lose" offer, right?