I've listened to audio books daily for the past five years. At night I drift off to sleep with an ear bud in and my iPod shut-off timer set for thirty minutes; a really good book, and I will reset the timer - more than once. All this listening requires a big supply of audio books.
Averaging thirty dollars a time this could be expensive but thankfully the local library has a large and ever burgeoning stock of books on CD. Ripping the discs is a bit time consuming but a little effort and some file manipulation provides a digital copy to keep.
Another free source is YouTube where rascals upload entire audio books and bask in a remunerative hit count until the Google Police pull their plug. Long in-print books slip through the holes in the net but recent publications don't stay online long. If you want to 'harvest' an audio file best conduct regular YouTube searches! I keep the Amazon books page open too for inspiration and to read reviews. Armed with a few bits of free software, a copy can be collected, trimmed into shape and on your iPod in under an hour.
Freemake Video Converter downloads the YouTube video, extracts only the audio element and saves it to your hard drive in any format you want; mp3 is for iPods.
Next, Audacity is a free audio editing suite with which you can split a fifteen hour file into bite-sized tracks.
With Mp3 Tag Editor you can apply titles, dates, authors, narrators and artwork.
Install a free audio book app to your iPod/iPhone and sync the audio files to your device.
With time and a little tenacity, your favourite book won't ever be due back at the library nor disappear from YouTube.