"Sacred Band" is the third and final installment in David Anthony Durham's "Acacia" Trilogy, as well as the best book of the three. Although not perfect, Durham improves upon the characters fleshed out so well in the second book, fixes some of the issues that were present in the first and second novels, and decisively concludes the story with emotional impact.
The book picks off not very long after the ending of "The Other Lands", with a narrative centered around the Akarian siblings. The Auldek are marching north and west to the Known World, with the intent of destroying its inhabitants for the sake of finding death and rebirth. Corrin Akaran, the Queen of the Acacian Empire and an increasingly powerful sorceress, plans to stop them - and to do so, she wields her magic in a way that I can't reveal because of the spoiler risk. Mena Akaran, her younger sister and great warrior, leads an army northward into the heartland of their ancient enemy (the Mein) to prepare for battle. Across the sea in the "Other Lands", Dariel Akarian is led westward to meet his destiny - and a fate that will re-shape the lives of the slaves left behind by the Auldek. Interspersed with these character arcs are a plethora of minor character stories, ranging from the traitor Rialus, to the scheming Leagueman Sire Dagon.
One of the issues with the previous installments of this series was Durham's tendency to lapse into his "omniscient historian narrator" voice, whereupon he would go into detail about the setting even when it didn't fit with the character point-of-view knowledge, or harmed the pacing. This is largely rectified in "Sacred Band", and use of the "exposition narrator" voice is fortunately limited. This helps in getting more emotionally involved with the characters, and there are many emotional moments in "Sacred Band" (particularly in the "Corrin" storyline).
The strength of the story continues to be in its major characters, and none more so than Corrin Akaran. She is wonderfully fleshed out and developed even further than in "Other Lands", and continues to defy convenient descriptions of "good" or "bad". She is ambitious, cunning, manipulative, and often close-minded . . . but also a devoted mother, ruler, and leader who learns from her mistakes, feels bad for the sins she has committed, and ultimately makes a great sacrifice for the sake of her children and her country. Although Mena and Dariel are strong characters in their own right, Corrin really stands above both of them in her complexity, emotional impact, and depth. Hers was by-and-far away the section most likely to bring me near tears.
That said, the novel does have some weaknesses. The minor characters are much more of a mixed bag when it comes to quality and impact. Sire Dogan was fascinating (mostly because he's fleshed out and humanized beyond our initial "scheming Leagueman" impression), but others characters, such as Melio, left me cold. The proliferation of minor characters also tends to be problematic when it comes to pacing - you find yourself following one storyline intently, only to suddenly be forced into reading through several disconnected view-point chapters in succession. Some authors can pull the story off with a huge cast (such as George RR Martin), but it doesn't quite work out perfectly in Durham's novel.
Another issue that I have with the book is that it really feels like less of a "character"-driven story than "Other Lands". The greater plot in "Other Lands" was almost entirely driven by the bad (and good) decisions of the characters, but "Sacred Band" feels much more "plot"-driven. The story arcs of Mena, Dariel, and Corrin are largely driven by outside plot elements, such as major events that happen to them. Of course, this is obviously a very subjective view, and you may prefer the plot-driven story.
My final concern with the book lies in the ending. While it's somewhat surprising and often quite emotional (particularly concerning a character whose name would be a major spoiler), it also feels very "pat". It's a little too neat in how all the loose ends are tied up for the best outcome (although to be fair, this was foreshadowed occasionally). This is particularly noticeable near the end, when some of the actions and capabilities of the main characters come perilously close to "out of nowhere" abilities.
All those issues aside, I found it to be a very solid book. It was addictive to read, and often quite emotional. I strongly recommend it for readers of the earlier books in the trilogy, and the trilogy itself for readers looking for an excellent fantasy series.