First Lord's Fury by Jim Butcher

In this book Tavi faces the ultimate challenge and the last battle for Alera against the Vord queen. He also must assert his rightful position as First Lord of Alera against a variety of challengers and rivals. Once again, Tavi's unusual upbringing allows him to be more resourceful and clever than his predecessors and his sense of honor and charming personality help him to earn the respect and cooperation of a wide variety of peoples. This book brought the Codex Alera to a fitting and enjoyable conclusion.