We use epub books and a phone app that reads them out loud.
"voice aloud reader" (no affiliation and there are lots of other similar apps available)
We had to play a bit with the voice selection to get one we like (we picked a light British accent in a woman's voice).
We then connect it to the stereo with the 3.5mm input but you could bluetooth it also.
It's not perfect but it's surprisingly good. Occasionally, it will put the emphasis on the wrong word but really very good.
It's nice because it's the rare book that you can't find in epub format as opposed to true audio books that someone has read.