Kingdom of Spirits by Alisha Klapheke

Her life, or her love. Tahlia can’t have both.
When Tahlia’s commander dies under mysterious circumstances, the only suspect is… Wait for it—their new commander.
Fantastic.
If Tahlia accuses her without proof, she’ll lose everything. Including her soul-bonded dragon.
To make matters worse, something is wrong with her handsome and perfectly grouchy captain. Marius won’t meet her gaze, and he won’t utter one word about the new commander.
Like, not a syllable. As if maybe he isn’t able.
But Talia can’t just walk away from him. This is Marius we are talking about. He is about to set off on some secret mission, and she can’t let him go alone when he has that creepy, clouded look in his eyes. Especially with the fate of the dragon riders resting in such dangerous hands.