Water for Elephants
Things get pretty hot and heavy in this book. For starters, we've got forbidden love and adultery. Jacob and Marlena simmer with sexual tension for about the first three-quarters of the text. They finally consummate their relationship just as the other events of the plot start ramping up to a climax. (Yeah, we went there.) Throughout the book, Jacob is upfront about sex, moving from curious virginity, to regretful exploration, to passionate consummation, and finally to rueful bemusement about his old body. He's the only character we see in both the past and the present. Characters like Marlena remain young, vibrant, and full of sexual energy because we never see them in old age.