Finally! I almost gave up on this once or twice. I was just not feeling the way Yelena bumbled around for 95% of the book. The theme of this book was that plans always fail.
Yelena is supposed to be learning about her magic, like she was supposed to be learning about her magic in the last book. But that plan is scrapped within the first chapter, which is honestly a good thing. Because I was horrified at the prospect of having to witness Yelena take lessons from Roze like Harry having to take Occlumency lessons from Snape. I just knew it was gonna be torture, so I'm glad that plan was tossed out the window. But all the other plans? As horrible and "let's-just-wing-it" as they were, never worked out. And that constant fail was kinda miserable to read. Nothing went right. Depressing.
I admit that the villain was a total shocker and I was bitch-slapped with that revelation, which I loved. No complaints there. The ending made the read worth it. I had such a hard time dealing with this story for a while because it seemed like everyone drank some stupid juice, but they redeemed themselves in the end and I finished feeling satisfied.
I'd recommend the series as a whole, but the first 3/4 of this book really tested my faith.