Alternatively, create special reports from your book content and give them away as teasers and bonuses to get customers to buy the full version or other infoproducts. Condense your special reports to 750 words or less and create articles in the area of your expertise for ezines and websites. This is a well known method of self promotion. At the end of your article, add a five or six line resource box promoting your infoproduct and include your URL and email address. See the resource box at the end of this month's guest article to see how it's done.
Audio books are popular and increasing in popularity among time-short people.
If you're writing fiction, audio books may be the perfect addition to your income streams. They must be done professionally however. No one wants to pay good money for an amateurish tape. You can narrate your own audio book if your voice is good. Otherwise, look for a trained actor or public speaker.