But I recently tried my local library's audiobook system. It's misleading:
It says "MP3" but it's actually a file ending in .ODM. A little Googling around shows that it works with a phone app called Overdrive:
It's a little bit strange to use, having you choose your local library and only then start downloading the book that you checked out. After you get it set up, though, it's terrific: automatically downloads several CDs worth of a book to your phone so you can play it all the way through without changing disks.
My first experience of this format was a book I read years ago:
So despite the slightly clunky interface, this is well worth trying ... I returned The Stupidest Angel so grab it quickly!