2014-2018 Mazda 3 Skyactiv Audio & Electronics
Seems, like infotainment system can recognize audiobooks files and display it in separate menu section.
So, I've try to put any kind of audiobooks with any kind of metadata to USB flash storage. Like mp3, mpeg, aac, m4b. aa. aax.
I've try to set ID3 tag "Genre" to "Audiobook", "audiobook"...