Self-help audio books are used for education. Self-help audio books range from public speaking to learning meditation. Self-help audio books are used to develop one's skills, to be happier, more successful in life. While some focus on a particular skill, others help to shift the listeners life entirely.
Audio books are considered a valuable learning tool because of their format. You can't read a book while you're driving, can you? On the other hand, audio books let you learn new things in many places you couldn't previously. Usually while doing mechanical skills not requiring much thought. Self-help audio books can be listened to while doing laundry, driving, exercising, sleeping.
For this 'miraculous learning' to take place, one might also need to listen to the self-help audio book several times. This is for the information in the cassettes/CDs to be absorbed fully. It's however very easy compared to reading a book many times. Some estimates say 21 times in total, 3-4 times a week is the time for the matter in hand to become second nature. An audio book heard only once will most likely disappear from the memory very soon as like any other sound heard only once.