One of the big ideas in Handmaid's Tale is reducing sex to less than the sum of its parts. Society has tried to eradicate pleasure and eroticism by depriving women of power and agency, and sex is supposed to only be a means to an end for sanctioned fertility.
That said, there's a lot of sex in this book. While some of it, like the narrator's encounters with Nick and her remembered time with her husband, is full of passion and pleasure, a lot of the sex isn't consensual. Much of the sexual activity is instigated and controlled by men, or people in positions of authority, and even if women aren't necessarily beaten or physically harmed, they are still coerced. About the "Ceremonies" which stand in for sex in her society, the narrator says they're not about love, pleasure, or rape:
I do not say making love, because this is not what he's doing. Copulating too would be inaccurate, because it would imply two people and only one is involved. Nor does rape cover it: nothing is going on here that I haven't signed up for. There wasn't a lot of choice but there was some, and this is what I chose. (16.7)
Shmoop would respectfully like to say there's potential for disagreement with this last statement. While the narrator did agree to become a Handmaid – and thus have sex with the Commander – we don't think the choice between that and death is much of a choice at all.