Audible received an update to version 1.5.1 today that brings in a handful of new improvements, such as the introduction of cloud storage of audiobook progress and bookmarks to the UK and Germany. In addition to that, the library filter and sorting preferences now persist after the app is closed. If you're using Audible on a device running Android 4.2 or earlier, you can stop here. But for those on 4.3, the best is yet to come.
If you want to listen to an audiobook, Audible is the number one source. Though, the app was never great on Android. It wasn't terrible, but it didn't have a strong Android aesthetic and the layout was strange. With the version 1.5 update, that's a thing of the past. The app looks excellent now, and there are other improvements too.