The app's design is alright; it's not ugly, but it's not all that great to look at either. The drop-down menu on the left side gives you quick access to all of Amazon's sections. However, this seems counterproductive since there are so many sections, it's almost distracting. In addition to Amazon Underground's apps, you can also find washing machines, books, televisions, video game consoles, etc.
Amazon Underground is an interesting alternative to Google Play that you can use to download all types of apps. The best part is definitely all the paid versions of apps that are offered for free.