The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Active Interest Media Inc:
4.1.0-New crop and share feature makes it easy for you to share engaging content with your social network-Efficient new gallery layout makes issue descriptions available with the flip of a cover-General speed, visual, and branding enhancements throughout the app