You are downloading the AT&T APS XAP file v188.8.131.52 for Windows Phone. AT&T APS is a free and useful Books & Reference app: This app is not for general use. It is for use by existing account holder only. You will have previously been issued an account - if you do not ... You can now download the offline XAP file to install & try it.
Download Locations for AT&T APS 184.108.40.206 XAP file
Note: To install it manually from an SD card, you should choose one of the server location above to get the offline AT&T APS XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.