The Shadow Throne by Django Wexler

The King of Vordan is dying, and his daughter, Raesinia, is destined to become the first Queen in centuries.
But politics knows no loyalties, especially for Duke Orlanko, Minister of Information and spymaster of the empire. The most feared man in the Vordan will bow his knee to no Queen, unless she is firmly under his influence.

Freshly returned from their recent victories in the colonies, Colonel Janus, Marcus and Winter must play a new and far deadlier game than the open warfare of the front, using all their talents, earthly or supernatural.