Currently I am reading Inhabiting the Cruciform God by Michael Gorman, which I also will be reviewing soon. I wanted to bring up one point that Gorman makes about holiness in sexual relations within marriage, that I don't think I'll have room for in my review.
One of the main points Gorman makes in his book is that Jesus self-sacrifice on the cross reveals God's holiness. Thus, other regard is at the core of what it means to be holy, for both God and us. This understanding of what it means to be holy clearly impacts what it means to have holy sexual relations. Holiness requires more than monogamy. It requires that we serve our spouse through sex. It's not about seeking your own gratification, but seeking the gratification of your spouse first.