My thanks to Clay Shannon for the suggestion that LibriVox audiobooks can be
loaded onto iPhones by downloading them to one's PC, then emailing them to
the iPhone. That particular suggestion didn't work for me because the audio
files are far too large to email. However, in the course of trying to figure
how to get the files on my phone, I hit on a solution: I installed
LibriVox's app (for $2.99) onto my phone, then used it to download several
audiobooks. These files aren't in the same folder as my Audible.com books,
but as the LibriVox application works much like Audible, that is a minor
inconvenience.

Now that I know a practical way to listen to these books on my
phone--something I do almost every time I drive my car, ride my bike, work
out at a gym, or do quiet yardwork --I'll repeat the suggestion I made in my
first posting on this subject.

Thanks to the generous volunteer work of people like fellow forum member
John Greenman, literally thousands of full-length recordings of public
domain books are freely available on LibriVox.org. As I said before, many of
the recordings are painfully amateurish, but others--such as those of
Greenman--have a professional polish that makes listening to them
pleasurable. If you've never listened to an audiobook, I strongly recommend
you give one a try, and I further recommend starting with a book with which
you are already familiar, as listening to a book attentively takes some
practice.

I know some people scorn audiobooks as poor substitutes for reading from
printed books. I think of audiobook listening not as a substitute, but as a
supplement to reading. I've read HUCKLEBERRY FINN in print many times and
have also listened to recordings of it an additional ten times. All this
listening has naturally helped familiarize me with the book, but it has also
done something else: Every time I listen HUCK FINN I get something out of it
that I don't recall noticing before. 

If there is a downside to listening to well-narrated audiobooks, I can't
imagine what it is. Moreover, the nearly 1,000 books I've listened to over
past 25 years have spared me thousands of hours of tedium when reading a
printed book would have been impossible.