Charmcaster (Spellslinger #3) by Sebastien de Castell
A failed mage learns that just because he's not the chosen one it doesn't mean he can't be a hero in the third book of an exciting adventure fantasy series from Sebastien de Castell.
Kellen's life as an outlaw spellslinger is about to get a lot worse.
In Gitabria, a miraculous discovery draws spies from all over the continent willing to kill to get their hands on it. Swept up in the race for power, Kellen is forced to join the pursuit. But the invention holds a dark secret-one that could spark a war.