Even though this thread is from last year, perhaps my method of quickly finding audiobooks for a new language will prove useful to someone
As a general formula:
1. Use Google Translate if needed to translate 'audiobook' into the target language (TL): audiobook -> audiolibro
2. Find the name of the book you want to listen to in the TL using Wikipedia or Google Translate:
Harry Potter and the Philosopher's Stone ->
Harry Potter e la pietra filosofale
3. Search on YouTube:
audiolibro harry potter e la pietra filosofale
I've used this technique for Russian, Ukrainian, and Polish. Less of a hassle than downloading an entire book, especially if you're just beginning.
On Android, I recommend installing
YouTube Vanced to get background playback in the YouTube app.