Ashes and Metal by Naomi Lucas

No one messed with Gunner. No one. He was the Jackal, living chaos, the infamous Cyborg banned from civilized society. He was also the only Monster Hunter for the EPED who took the hard jobs, the under-the-table work. Jobs that often left a trail of blood and bones in their wake. When a pirate commandeers his ship, Gunner takes it upon himself to exact a revenge that will ignite a wildfire of rage, death, and torment upon those who made the mistake of taking what was rightfully his.

Elodie has spent most of her life pretending to be a boy to remain alongside her father in space. He’s the only family she has left. When the ship they worked on is attacked, she’s taken prisoner. Every day, she feared that her secret would be discovered—that she’s a woman alone amongst men. When a strange man is dragged into the cell next to hers, she realizes she was living on borrowed time. He stared at her as if he knew her secret…