A Peace Divided
Here is a 2017 title by Tanya Huff, A Peace Divided.
It is #2 in a Trilogy, which is a follow-after series about Gunnery Sergeant Torin Kerr, hero of the 5 Book Series that starts with Valor's Choice where she is a Staff Sergeant.
She is a Space Marine, through and through, complete with her opinion of the Space Navy.
I would suggest reading all these novels -- Tanya Huff is just one of those bylines you grab without reading the back of the book to find out what the thing is about. She's just that good a writer.
However, simply as a stand alone novel, A PEACE DIVIDED works fine. It is one long drive toward completing the mission of rescuing hostages. The hostages predicament is a result of the various war-stories in the 5-book series VALOR.
But it's simple enough to understand as a plot driver.
The important thing for Romance writers is to plumb the depths of the Relationship (yes, love, but camaraderie and respect and reliance, and much more) between Torin Kerr and her exemplary Pilot with an ego from here to there and back.
This is not a Romance, but it is Relationship portrayed with speculative potential you must not miss.
Gunny Kerr has mustered out of the Space Marines - where she was trained and conditioned to solve problems by destroying things and people as necessary -- into the PEACEKEEPERS where destroying things is frowned on and destroying people forbidden (and the definition of people has been enlarged.)