You are downloading the Audible APPX file v126.96.36.199 for Windows Phone. Audible is a free and useful Books & Reference app: Not enough time for all the books you want to enjoy? Download the app by Audible.com, an Amazon company, to listen to books on the go. ... You can now download the offline APPX file to install & try it.
Download Locations for Audible 188.8.131.52 APPX file
Important Notice: Now Due To Unspecified Limitations, You Can Not Use The Offline APPX File To Install It Any More.
To try to install it manually from an SD card, you should choose one of the server location above to get the offline Audible APPX file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.