Writing a book can help attract customers to your business in several ways. It gives you credibility as an expert, provides free advertising when you appear on TV or radio to discuss your book, and helps you differentiate yourself from competitors. Specifically, one dentist promoted his book to existing patients to get referrals from their friends. Another author used his book to build rapport and recruit members for his direct sales organization. Overall, writing a book can make you a "magnet" that attracts more prospects and boosts your income and referrals.