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"