Amazon is touting this as a "beautiful new design", but so far as I can tell this isn't new so much as a refresh. The interface now incorporates design elements found in the current versions of Android, including the slider bar, tabs, buttons, and the like.
The app also reportedly has a simplified library management and has been reorganized to improve navigation.
I have also noticed that Amazon has made a subtle change to their badge icons. The badges, which can be earned for various activities inside the app, are now flat icons and not faux 3d icons.
What's new in version 1.5
• Beautiful new design
• Improved navigation
• Simplified library management
• Chapter-level progress bar in the player
• Improved stability and performance
Audible has dominated the downloadable audiobook market since before Amazon bought it, and that doesn't appear to be changing anytime soon. What with Amazon's efforts to integrate Audible more closely into the Kindle platform (Whispersync for voice), Audible Creation Exchange and that marketplace's domination of the self-pub market, and Amazon's ongoing efforts to find a new price point for audiobooks, Amazon is set to dominate this market indefinitely.