My daughters download books from the internet and listen to them in the car and at home. They use their i-phones and their i-pads which can be plugged into their car stereos.
Have you checked with your friend to make sure he likes the idea? My mother tried to arrange it for my grandmother when her sight was severely diminished, and they really were books on tapes, and my grandmother did not like it at all. She said she would prefer to listen to movies than to be read to. Also, are you sure he wants to use earphones? Maybe a headset would be more comfortable.
How old is your friend? When my husband (62 yr. old) had eye surgery last year, a friend loaned him an i-pad with all the Harry Potter stories on it and he loved it. He had seen the movies but never read the books. When my FIL had the beginning stages of dementia, he liked reading biographies. Things that didn't have a lot to remember.
Good luck. You are being a very good friend.