iPod's Audio Book Features
Your iPod provides some nice features for Audio Books.
Remembering the last listening positionBecause audio books are most of the time quite large files, it's unlikely that you listen them in one piece. Your iPod remembers the position where you stoped listening the last time. So when you continue listening to your audio book, maybe days later, you don't have to waste time finding the right position to start. This even works, if you are listening to music or other audio books in the meantime.
Adjusting the reading speedYou can adjust the reading speed to your personal preferences. This seems not that important to me but it can be useful in certain situations.
Unfortunately these features are only available for audio books in the iPod format (.m4b) but not for MP3 files. Thats the reason for the existence for this converter software. Please refer to your iPod documentation for more information on how to use these features.