The Alien’s Cruel Starfrost Domain by Margo Bond Collins

If she escapes and lives, his kingdom will be destroyed. If she stays and dies, his heart will be demolished.

Sold by her stepfather to Duke Ivrael of the Caix, a race of fae-like aliens, Lara Evans’ biggest fear is realized. Now, she will stop at nothing to save her sister Izzy from a fate worse than death.
But Ivrael sees the Evans sisters as key to saving his dying civilization. He believes he can use Lara and Izzy to prove his theory that technology and magic can coexist—and to overthrow the kingdom’s current cruel ruler.
As their mutual distrust gives way to dangerous attraction, both find their plans unraveling. With Izzy’s fate approaching, Lara must decide between betraying the duke and saving her sister. And Ivrael will either have to sacrifice the sisters to save his world… or risk everything.

If you loved the spicy aliens of Ice Planet Barbarians, the court intrigue of Cruel Prince, and the morally grey hero of Fourth Wing, The Alien’s Cruel Starfrost Domain is your next addicting read.