Wow! Impossible to say!
Most major public libraries have downloadable audiobooks. Just enter your card number and plug in your earphones. I listen to non-fiction, and sort by most popular. Download more than you think you have time to read, so that if you get a dud, you can move on to something better without stopping.
I listen to books while I work, (yeah, I'm one of the pre-retired RVers) and have been listening to books for nearly two years, and am far from exhausting the available books.
1989 Avion 34VB, "QE3"
2008 Toyota Sequoia 5.7L "Tug"
(Is there no respect for an 8-ton GCVWR truck? *sniff* )