A Choice of Treasons, science fiction by J. L. Doty

As a lifer in the Imperial Navy, fighting in a war that has lasted for generations, York Ballin’s only hope at an honorable discharge is the grave. Matters only get worse when the emperor's daughter, princess Aeya, decides to do a little slumming with her entourage on a remote planet, and York and his fellow crewmen are forced to rescue her. But after returning her safely into the empress' care on the planet Dumark, the entire planet is hit by a massive Directorate assault. To evacuate the empress along with the rest of the imperial embassy, York is ordered to commandeer the imperial cruiser Cinesstar, which is crewless and undergoing repairs in the Dumark Navy Yard. And after a narrow escape York finds himself deep behind enemy lines, on a commandeered imperial cruiser without a trained crew, commanded by an incompetent nobleman, with the empress and 200 civilians as passengers, and the enemy, the Directorate, pulling out all stops to destroy them. But, from a strategic or military standpoint, the assault on Dumark was an unwarranted waste of the Directorate's resources, and it becomes clear the empress, and a member of Aeya's entourage, are carrying a dangerous secret, so dangerous it threatens the power structures of both the Empire and the Directorate, so even their own comrades in the empire want them eliminated. And with everyone now hell-bent on turning Cinesstar and all those aboard her into a cloud of radioactive vapor, it falls to York to save them all. But he must choose between saving them, or saving himself, and he finds his options are limited to a choice of treasons.