What is the theme in The Art of Courtly Love by Andreas Capellanus?

Book two focuses on how to keep love once one has found it. However it covers a number of other related issues such as how to increase love or decrease it. Chapter 1, 'How Love, When It Has Been Acquired, May Be Kept' focuses on the main topic of the book and from there the subject matter branches off. In chapter two, 'How A Love, Once Consummated, May Be Increased' explains how a man can interact with a woman to get her to love him more and in chapter three, 'In What Ways Love May Be Decreased' Capellanus reviews all the factors that threaten the intensity of love. Chapter four, 'How Love May Come To An End' explains all the different factors that can kill courtly love.