You could sell more of your books if you can answer two questions honestly. First, how often do people think about your book? Second, how often do people think about their own problems? You will probably agree that people think more about how they can solve their problems, learn something, improve themselves or be entertained than they do about your book. However, if you can show them how they can help themselves in some way by reading your book you are likely to increase your sales and revenue.