Why another marriage book? There was need for an audiobook with short, practical chapters with assignments and suggested prayers so that people could listen for a little while and grab hold of something that they could apply to their marriage right away.
The chapters needed to be short enough that husband and wife could listen together without too much inconvenience, enjoy the time together, and even discuss the content. The fact that the lessons are so practical, and, therefore, immediately applicable, is huge.
The assignments give direction as to the application. Then the icing on the cake: for the husband and wife to pray out loud what is suggested at the end of each chapter, brings a real sense of honesty before each other, and before the Lord.