Exactly how steamy is this story?
PG-13
We're mostly dealing with references to sexual behavior in this book rather than descriptions of the full monty. The larger issue is that the sexual behavior mentioned generally has a violent or unwholesome nature.
Mac and Jim talk about visiting prostitutes (some of the workers discuss their desire to save up enough so that they can), and the workers complain about STDs running rampant in the housing units in the orchard.
Mac also tells Lisa that if she hadn't just had a baby, he'd basically rape her. Lisa constantly refers to her recent motherhood and how she's "not like that" to keep the men at bay. Jim encounters a lovely woman in the camp and is turned on by how she brushes her hair. She has to tell him "No" before he utters a word.
Overall, the sexuality in this work really just leaves you with a mildly icky feeling—which is quickly forgotten once the hardcore violence comes in.