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

Each of the three books has a well-defined theme. Book One is the introduction to the treatise and it starts where a treatise on love naturally begins, explaining how love is acquired. Capellanus begins by explaining what love is and the various forms of love, their effects, and the people who should engage in the practice of courtly love. However, the primary element of importance in the acquisition of love is the initiation of courtly love.