His Human Conquest by Stella Rising

When she is taken captive by elite warriors preparing for an invasion of Earth, scientist Jillian Wexler assumes they are interested in her expertise with deep space monitoring, but she quickly discovers that the huge, handsome alien who leads them has plans for her beautiful body as well.

Commander Vol of the Dominars needs a liaison with the people of Earth, but Jillian will be much more than that. She will serve as an example for the rest of humanity of both the obedience expected of them and the pleasure which can be found in complete surrender to their new masters. He will make her his pet, first training her thoroughly and then using her as he pleases.

Jillian soon learns the hard way that defiance will be sternly and shamefully punished, yet even with her cheeks blushing and her bottom sore both inside and out, she cannot hide her intense, helpless arousal. But though Vol’s rough, dominant lovemaking leaves her utterly spent and satisfied, can she allow herself to fall in love with an enemy intent on conquering her world?