The Customer-Driven Company - Moving from Talk to Action" by Richard C. Whiteley (published 1991 by Addison-Wesley Publishing Company).
To succeed in business, entrepreneurs have to treat every customer well. The lifetime value of a software customer is much larger than the cost of a single-user license. Satisfied customers buy software upgrades, and they tell their friends about your application.
"The Customer-Driven Company" is a practical guide to delivering top-quality customer service to your clients and prospects. Whiteley believes that there are two types of companies: companies that consistently deliver excellence, and the companies that fail and go out of business.
"The Customer-Driven Company" has a lot of good insights, case studies, and checklists. It nudges entrepreneurs to think about our attitudes toward our customers and prospects, and our willingness and ability to react to the marketplace.
"The Customer-Driven Company" reminds us that we have to ask customers for their feedback. If you don't have many management books on your shelf, this is a good one to add. Even though Whiteley doesn't specifically address the software development industry, the book can help you with your software marketing.