Surprisingly good, this one. One container, and it's away! The apps lets you download the audiobooks for offline use (also to existing folders on Android, in-case you have a preferred audiobook app). This means that you can run the server on-demand (eg. when your laptop is on). Thumbs up.
For some almost-certainly-anti-competitive-reason-that-should-be-investigated-by-the-EU-and-other-watchdogs, Amazon refused to let it onto the Amazon appstore, making it a no-go on Amazon Kid's tablets/profiles.