Blade Broken. The Echelon, #1

A spy lurking in the shadows, a nation on the verge of an invasion, a man desperate to protect his home. Lucian is the Blade of Castrial, the kingdom's spymaster and first line of defence, lauded for his success in repelling an invasion from Garaner. But the war has left Castrial's economy in shambles, and when the neighbouring kingdom of Sarian musters their armies and sends spies into Castrial, Lucian realises two things: they have a spy in their midst, and they can't afford the cost of fighting off another invasion.
And if that wasn't trouble enough, there is Alaric, the Shield of Castrial and the only man in the Echelon whose power is equal to Lucian's. Returned from banishment like the vengeful spirit of their long-lost relationship, Alaric carries a deep-set grudge against Lucian, a grudge that may well be justified. Lucian's desire to protect his nation is nearly equal to his wish to reconcile with Alaric, but if he cannot get his act together and convince the Shield to work with him, Castrial will fall.
Blade Broken is a queer, sword-and-sorcery fantasy and the first book in The Echelon Series. If you love flawed characters, betrayals and redemption, and gritty worldbuilding with lots of political machinations, you will love this book.