Hellfire by Jean Johnson (Theirs Not to Reason Why #3) is currently $1.99 in the US
https://www.kobo.com/us/en/ebook/hellfire-9
https://www.amazon.com/Hellfire-Thei.../dp/B009RYS0PW
This is a middle book in the series and I would recommend starting with the first book but otherwise I would recommend this book and the whole series
Her story began in the national bestsellers A Soldier’s Duty and An Officer’s Duty. Now Ia is captain and commander at the helm of Hellfire, where she is finally free to chart the course for the fulfillment of her destiny…
As captain, Ia must now assemble a crew that can rise to the ultimate challenge of saving the galaxy. The hardest part will be getting them to believe her, to trust in her prophecies. If they don’t, her own crew will end up being the biggest obstacle in her race against time.
The Salik are breaking through the Blockade, plunging the known galaxy into war. Ia cannot stop it this time, nor does she want to. This is the terrible price she has seen all along—that some must pay with their lives so that others might live. Now only time itself can prove whether each member of her crew is merely a soldier or truly one of Ia’s Damned.