This review will contain spoilers!
In many sentences:
There's no other way to say this than Brilliance of the Moon is a disappointing book. I've thought a lot about why this is - why did I enjoy the first book so much, but the second and third so little? I think part of the answer is in the question itself: I really liked the first book, so my expectations were high for the rest of the series. Ok, that's fair, but why did the second and third not meet my high expectations? In the first I enjoyed the magic and mystery surrounding the tribe abilities, I enjoyed watching Takeo learn about them and himself, and I enjoyed the tension surrounding the decisions he was forced to make in respect to the teaching so Shigeru, the Tribe, and his mother.
In this book, however, there is no discovery or mystery surrounding the abilities. They are suddenly taken for granted. Perhaps Takeo doesn't find them as interesting as they could be, but there are numerous other characters who do. A great example is Taku, the son of Shizuka. At one point Takeo even remarks about how he wants Taku to be the first of many children spies. Now that sounds interesting - why not pursue the avenue of Takeo as the teacher instead of the student. How would he teach compared to the Tribe? Would he instill compassion and mercy in his students, instead of the cruelty he was taught by the tribe? This is a much more interesting dilemma compared to hundreds of pages of Takeo running from Arai.
Not only is the running far more boring than any discussion of the Tribe abilities would be (even if it's just a philosophical analysis of how they are possible. When confronted with this question, though, Takeo just tells Hiroshi that some things cannot be taught. Way to brush off a great question Takeo!), but the resolution itself is horrible. So we've just spent TWO books wondering what will happened when Takeo confronts Arai and the Kikuta master, only to have Arai shot at range with a firearm, and the Kikuta master to be killed with the help of Taku and Kenji. Then everything works out perfectly, how convenient!
In all honesty, I think this book and the second would have worked much better as 100 or so pages used to introduce a book that deals with Takeo's struggle of becoming both a warrior and Tribe leader for the Three Countries. How would he handle the warrior code, his Hidden beliefs (or at least their impact on his personality), and the Tribe code? Could he pass all these ideals on to others, as a part of bringing peace to the land, as the prophesy predicted? Such a tale would be far more interesting in my opinion.
My least favorite aspect of Brilliance of the Moon, however, was the way Kaede ending up with Fujiwara was handled. Under what scenario would this intelligent, brave young woman be stupid enough to return to the man who practically held her captive in the previous book. What did she expect to happen? Don't get me wrong, I'm not heartless. I care that these characters are facing sorrow and death. But the circumstances surrounding her being married off to Fujiwara felt so artificial that I found myself annoyed about my compassion rather than engaged with the story. It felt like Hearn needed a reason to send Takeo to Fujiwara so he could be captured by Arai, and so she had Kaede act like a fool and get herself captured. Nevermind that it was fabricated, it was necessary for the plot.
I also think the last line: "But my death is another tale of the Otori, and one that cannot be told by me" (328) is a complete copout, especially since half the book is told from the third person perspective.
As I said at the beginning of this critique, it is the lack of fulfillment of potential that makes this book so frustrating. Hearn is clearly a skilled writer (see Across the Nightingale Floor) but, for me at least, she completely missed what made her first book great. Unlike the Bartimaeus trilogy, where the third book is the culmination of all the characters, events, and techniques of the previous works, Brilliance feels like nothing more than the faint echo (or rather a moon shadow) of the first book. I do not recommend it. In fact, I encourage you not to read it, sticking with the first of the series only.
Lian Hearn the Last Line of in Brilliance of the Moon