As my GPS unit has the ability to play MP3s and audio books through it's internal FM transmitter to my FM radio I've been downloading audio books from various websites that offer them for free download.
I've found them to be a great way to pass the time while driving over long distances. There are a wide variety of genres to download and anyone can find something to suit their taste. Most are classics which are always nice to revisit from time to time. I'm especially fond of the Sherlock Holmes books and others of that mystery genre.
This is somethng to keep in mind if you're planning to take a long trip. Download some audio books and take them along for the drive. If you don't have an MP3 player that will work in your car you can always burn them to CD and play them that way as most CD players these days are capable of playing MP3 files. If not, there is a lot of free software out there that can convert them over to standard CD format.
It's amazing how the miles just fly by when one is listening to an interesting audio book.