I just read chapters 9 & 10 about "Roles" and "Sexual Conduct". I love the theology that is presented in these chapters. Mary Kassian does a great job with both of these subjects. I commend this book and these two chapters to you. I'll leave you with a quote from chapter 10 (page 141).
Marriage is about family--a husband and a wife establish a new family unit. Their union produces children. The relationship is a symbol that teaches us a lot about God. It teaches us about the relationship a father has to his children. It helps us understand the relationship between God the Father and his only begotten Son, the enormousness of what it meant for the Father to sacrifice His son, and what it means for Him to adopt us as His children (Romans 8:29, Galatians 4:5-6).