Book 4 of the Codex Alera takes place two years after Tavi took command of the First Aleran and led his troops to their first victory against the Canim. Since then it's been a furious to and fro not just between the Canim and the Alerans, but pushing back against the rebellion of Kalarus. Tavi's Aunt Isana knows the time has come to tell Tavi of his true identity, but is terrified of the repercussions, not least because of her position as his mother, but also because Tavi will immediately become a target for those scrambling for the First Lord's seat.
Meanwhile, the First Lord himself has picked Amara and Bernard to come along with him on a secret mission to enter Kalare, Kalarus' domains, and essentially show Kalarus who is boss.
This book goes into the politics of warfare at greater depth, and it's fascinating to translate the idea of these war committees into real life. Egos and agendas rage, and tough decisions about thousands of people's lives must be made. Tavi wants to save as many Alerans and Canim as possible - he suspects exactly why the Canim left their homeland in the first place, and it wasn't because Alera suddenly became oh-so-appealing - but Senator Arnos, officially in charge of the war committee, wants all-out bloodshed.
The character development I love most in this book is Kitai's. As we get to know her through Tavi, we learn more of her sharp and ready wit, her heart, her black and white view and her general bad-ass-ness. Similarly, Araris, who we met first as Fade, is finally allowing himself to drop his slave persona, as well (at least partly) letting go of his guilt and shame of the events in which Septimus', Tavi's father and the old Princeps, was killed. And for Amara, the veil is torn from her eyes as she sees exactly how far Gaius is willing to go in order to keep his realm together, at whatever cost. After implicitly trusting someone so much whom has sent her into mortal danger time and time again, this is a pretty significant part of the book, and it'll be interesting to see what she does from here.