Into the Black — Ava Jae

The world ruler is dead, technology foundational to their society destroyed, and Safara is on the brink of collapse. Half-human, half-alien Eros is the rightful heir to the world throne, but before he can return to the capital, he's abducted by a rebel group of humans who call themselves The Remnant―and won't release him until he swears to help them overthrow the very government he's inheriting. With Eros missing, ex-queen Kora is determined to stave off mad grabs for the throne. But as royalty from across the territories flock to the capital, and a new charismatic candidate takes the spotlight, Kora sets off into the desert with a skilled prince-turned-bounty hunter to find Eros before it's too late for both the future king and his kingdom.