This is book four in the Codex Alera series. Start at the beginning with Furies of Calderon. The important characters are all ongoing.
I liked this series from the start, and it just keeps getting better. It's the same flavor as the past books. A couple of the major pieces of the story arc have fallen into place, perhaps inevitably but satisfyingly. There is great heroism, exciting battles which are made interesting to the jaded reader by magic, touching romance, and some good plot twists. There's a lot going on but I felt more able to stay on top of it than in the earlier books. There are a couple of weak points. Magic doesn't seem to be limited by much except the convenience of the plot, and it might be hard to swallow if you weren't in a mood to go with it. And there are a couple of tight spots where the characters only seem to escape by cheating. But there's only one place where it actually bothered me even a little bit. This world is so vibrant, the characters so much larger than life and yet still real so that I can empathize, the action so riveting, that if I were a faster reader I wouldn't have put it down. I did take a week to read it (I've been busy), but I seldom feel so eager to get back to reading my book as I have with this one.
10 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
In one main plot line, we pick up on Tavi, still operating as Rufus Scipio, has kept the First Aleran alive and made slight gains against the Canim in the two years he's held the Eilinarch. He's also been practicing furycraft in secret with Kitai, and can effectively use metal, earth, and windcraft in battle and read emotions with water. Senator Arnos, a politician and a well trained military academic with no clue about real fighting, shows up with a couple of newly minted legions. He's the political pawn of Aquitaine, and Invidia is directly supporting him. Gaius shows up and orders "Scipio" to try to keep Arnos from ruining the war while keeping him in check, and then disappears on an undercover mission. Arnos quickly takes a dislike to Scipio after Scipio makes him look like the fool he is. Arnos is trying to win glory publicly for political purposes, and assumes it will be a trivial task to eliminate the 60000 Canim on the field. He wants an excuse to remove Scipio, who seems like a future threat. Fidelias (who is in disguise as Scipio's First Spear Marcus) suggests that Arnos order Scipio to execute some innocents so that he will disobey orders. Fidelias didn't expect that the innocents would be the whole population of a town that had been taken over the by Canim. Tavi has his people delay the execution by painstakingly checking the citizenship of each of the condemned while he slips off to parlay with Nasaug, the Canim commander, against Arnos' direct orders. Tavi understands that the Canim want to go home, and gets Nasaug to agree that if Tavi can produce Varg, Nasaug will consider a negotiated settlement. Arnos' spies see him leaving the meeting and Tavi's arrested for treason. Tavi manages to be in the middle of hundreds of troops personally loyal to him at the critical juncture. He uses the threat of an open mutiny that would destroy the campaign to force Arnos to agree to call of the execution and remand Tavi to the custody of Cyril back at Eilinarch. Then Isana, Araris, Kitai, and Ehren break him out of prison. They can't get an air coach for any price, so they hire Demos and the Slive to take them by sea. Arnos' elite bodyguards arrange to catch them on the seas with a bigger ship, but it's right in Leviathan's Run, the place where all the adolescent male sea monsters go to hang out. Isana takes the others on a secret submarine mission to kill the witchmen who make the other ship invisible to the leviathans, and in the process discovers vast new depths to her watercrafting ability. The leviathans destroy the other ship and Tavi makes it to Alera Imperia, where he pulls off a daring raid on the Grey Tower. (This is the impregnable prison that he sprung Max from two books ago. Since then, it's been upgraded, in large part based on his own report.) They return to the war. Varg beats Nasaug in a fight to convince Nasaug that their crazy plan needs to go forward, and we learn that the reason Varg was so important is that he's Nasaug's father. The Canim are unwilling to consider dealing with the Alerans because of the atrocities Arnos has visited on the countryside. Tavi gets them to agree that if he can deliver Arnos, the Canim will surrender, not to Alera, but to him personally. (They would surrender, even though they are winning on this battlefield, because eventually the rest of Alera will come along and wipe them out, or they can be eaten by the leviathans if they try to get back by sea. Although it never came up when they first came in by ship; I guess we have to assume that Sarl's magic had kept the leviathans at bay. It sounds crazy, but it allows both sides to achieve what they really want.) Tavi then returns to the fortified ruins where the Canim have treed the beleaguered Aleran forces and are about to wipe them out. He openly declares himself Gaius Octavian and calls Arnos to the juris macto. Then we find out that Phrygiar Navaris, probably the best swordsperson in Alera, didn't die when her ship was eaten by leviathans, and Tavi has to face her as Arnos' champion. He proves that his intensive training with Araris (who is the second-best swordsman in Alera) is enough that he can hold Navaris off long enough for him to use his brains. He works out that the reason she's such a crazy bitch is that she could never get the approval of her father (her surname ending in -ar means that she's a bastard), and he throws this at her when they're at a standoff and she cracks. He kills her when she attacks emotionally. Then we see Fidelias, who is supposed to snipe Tavi after he wins with a captured Canim balest on Invidia's orders, grab the perfect opportunity to put the bolt through Invidia and Arnos both, doing the just thing and also taking out the patron who had a hold over him. Arnos, who stays dead, is handed over to the Canim, who agree to the surrender. Then Gaius shows up, rather upset with the deal he's been maneuvered into, and signs the decree that will grant the Aleran slaves the Canim had freed and armed amnesty in exchange for accompanying the Canim back to Cania to fight the Vord. The amnesty is carefully worded to also include Tavi and his escapade breaking Varg out of the Grey Tower. Gaius and his grandson acknowledge each other with guarded respect if not real affection. (Gaius, though at least partially a good guy, is the most ruthless character in the whole series.)
The other main plot line is the mission Gaius went on. He recruited Amara and Bernard to take him secretly through Kalare. Kalarus has set up an extensive magical sensor network to detect any furycrafting from Gaius, and he's carefully patrolling the air, so they have to sneak in overland. It's a long, hard slog. Right at the start, Gaius gets blisters on his feet and just sucks up the pain until he has life threatening sores, and they don't have a healer since Gaius can't heal himself without giving himself away. With much derring-do they get to the strategic location. Gaius shows off a truly absurd amount of power as he personally wipes out an entire legion. Then he does what he came to do. Alerans all swear by Great Furies, but only a very few are aware that Great Furies really exist. They're too powerful to be controlled by any human, even Gaius, but Kalarus has stirred one up and then set spells in place so that when he dies, it will go on a rampage. Oh, and "it" is a major volcano next to Kalare city. Gaius' end run against Kalarus' mad plan to trigger an eruption that would destroy half of Alera is to trigger the volcano himself in a more limited way that only destroys the city. When Amara sees what he's done and realizes how he tricked her, she resigns her post as a cursor in disgust.
To recap the ending, Tavi, now openly Princeps Gaius Octavian, has ended the war with the Canim and arranged to spend the next year on campaign in Cania where he will be out of reach of the assassins who won't approve of Gaius having an heir while he (hopefully) comes into the whole furycrafting power of a First Lord, and Fidelias, who has now turned a traitor to Aquitaine and is secretly backing Tavi again, though he can't tell anyone who he really is, has seriously brown trousers because Invidia's body has disappeared from the morgue. (This is the one thing that annoyed me. The healers assured us she had a very serious case of dead before they put her in the morgue.)