This book is military science fiction, with a galactic imperial flavor to it. In a way, it feels like a combination of Robert A Heinlein, who was contemporary (more or less) with Gordon Dickson, and Lois McMaster Bujold’s Miles Vorkosigan books, especially The Warrior’s Apprentice and The Vor Game, which focus very heavily on Miles’s military career.
This book begins with the graduation of Donal Graeme from a military academy where he has achieved the status of “Dorsai, of the Dorsai” a high-ranking military position that has a bit of aristocratic/legionaire kind of feel to it. There’s clearly a heavy political element to the role, especially as he’s selecting what branch and path he wants his career to take. He becomes almost immediately enmeshed in political intrigue that leads to some dangerous choices.