Thanks for posting this. I've been waiting for this sale so I could spend some of my Amazon Coins. I already have two of these guides (free apps of the day), so I picked up the remaining five that Amazon sells. They only have 7 of 23 available field guides. Apple is the only store that has all 23 apps and Google Play only has 9 of them.
The one I wanted the most was the Pacific Northwest Nature Guide. Unfortunately, it's an iOS only app; so I'm out of luck.
This is a great way to spend Amazon coins, especially with a deadline approaching. Last year's introductory promo of 500 free coins
expires on 31 May. If these coins aren't spent by then, you'll lose them.