This is book 5 in the excellent Alera series. You definitely need to start at the beginning to know who these people are and how they got there. We're right in the middle of a lot of really scary stuff, but unlike some authors, it seems like Butcher tries his best to stop at a good place in the middle of the absolutely non-stop story arc, rather than at the very worst possible place.
There is just too much carnage in this book. But it sure does provide a great backdrop for the heroes to be heroic against, and they certainly rise to the challenge. They should be way over the top, but they have, and continue to hold, my heart so tightly that I'm wholly engaged. Magic is really powerful in this world, but it has enough limits to remain convincing, and the bad guys are really nightmarish. It would all be good fantasy anyway, but the best part continues to be the Canim, the most important non-human race. Their wonderfully alien psychology, and the way we use it to probe what's really important about people, would probably appeal to me a whole lot even if they weren't given a physical appearance that really pushes my buttons.
This volume isn't as good as the last couple. But I couldn't actually tell that while I was reading; I was far too deeply engaged. The series as a whole continues to be superb. 8 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
Tavi has set sail with the Canim fleet back to Canea. The fleet is caught in a huge storm and blown hundreds of miles off course, so that rather than winding up in Narasha, Varg and Nasaug's home range, they end up in Shuar, which is very hostile to Alera. Tavi and Varg bluff their way into being allowed to land and are taken to see Lararl, the guy in charge, a few days away, where they learn that Shuar is fighting a losing war of attrition against the Vord, and by implication that all of the rest of Canea has already fallen. Lararl has a few thousand Narashan refugees that he's using to fuel his ritualists' blood magic. Tavi conceals this from Varg to allow things to stay civil, and manages to maneuver everyone so that he can kill one of the two Vord queens and get all of the surviving Canim back onto transports -- three enormous barges made from icebergs. There is a touching reunion between Varg and his grandchildren, whom Varg assumed already dead. The Canim psychology is so deliciously well done that we're still not exactly sure how Varg feels about Tavi, but it's certain that he, and through him the rest of the Canim, will personally trust Tavi enormously farther than they would ever trust any other human. Tavi is pretty much the last person off the pier, and he gets caught in the water. Kitai rescues him and he falls back into the water, and then the figurehead of the Slive rescues him. At the very end of the book, Tavi has a brief meeting with a goddess.
While this is shaking down, we discover that the Vord have gotten a foothold in Alera, in the chaos created by the destruction of Kalare. The Vord have discovered how to use the discipline collars that made Kalarus' immortals possible to control Alerans, including Citizens, and this gives them access to furycraft. They also have Invidia, palling around with the Vord queen. Gaius is doing everything he can to hold them back and it's not enough. He sends Isana to the Wall to tell Antillus Raucus to make peace with the Icemen (they've only been continuously at war for 500 years) so the Legions on the wall can be freed to fight the Vord. Isana discovers that the reason the Icemen have always been so hostile is that the Alerans up there always use low-level firecrafting to stay warm, and fire is anger. Isana challenges Raucus to the juris macto, and manages to understand Raucus and to get him to see reason, after he's already put a sword in her guts. It seems that Raucus and Septimus were best buds, and both of them got involved with peasant girls and had sons, but Raucus wasn't willing to actually marry his girl and acknowledge Maximus, and he's kinda bitter that Septimus actually married Isana and that her son is now the heir. The legions arrive just in time to see Alera Imperia fall and Gaius call up another volcano to destroy it, and a lot of the Vord.
Bernard and Amara were scouting behind enemy lines, spying on the Vord queen and Invidia. Amara finds Rook. Kalarus Brencis, himself enslaved, is keeping the secret of the discipline collars to himself, so when Amara kills him, the Vord should, in theory, have no further supply of enslaved furycrafters. They, with the hundreds of Alerans they rescued while they were waiting to be fitted with collars, find their way past the fiery hole in the ground that was Alera Imperia to report their vital intelligence to the First Lord -- only to discover that the First Lord is now Aquitainus Attis, who says that while Tavi may be the legitimate heir, he's not there and Alera has to have a strong first lord *right now*. And he's so right that Isana agrees to support him on an interim basis until Tavi can return.
Now it's inevitable that Tavi and his Canim horde are going to save the day in the battle against the Vord; the Alerans have only one a brief reprieve, not any kind of a victory. Fortunately, it's not inevitable just how he's going to do it, or exactly how he will get Aquitaine out of the way and become First Lord, or whether the next book is actually going to be the end of the series.