Middle books are so tough, guys. They're sometimes called 'bridge books' because they are the in-between that connects the fresh, new first-in-series setup with the big-finish climax of the final book. It can be difficult for an author to find balance in the space between, delivering all the important big-arc buildup for book 3 or 4 without letting the story become a snooze-fest. (I'm battling this myself...) Needless to say, there's a reason they call it the 'book 2 curse'.
That being said, I think Pearson handled it well in a lot of ways. There is a lot of court-style tension in this volume with the introduction of the Komizar, an antagonist who has a depth of character that goes far beyond the 'big baddie' so often seen in fantasy. Lia's struggle to survive in Venda beneath the Komizar's sharp-edged attentions keeps the reader on the edge of their seat. Disobedience has consequences and Lia feels the sharp sting of them on more than one occasion.
The development of Lia and Rafe's relationship is, in my opinion, one of the most well-done aspects of this book. Lia's resentment over Rafe's deception is authentic, but not dwelled upon incessantly. They soon move past it in the face of their overwhelming circumstances and wisely put their minds to better use. Over the course of their captivity, their bond is constantly tested in ways that make your heart ache for them both. Rafe's restraint and Lia's cleverness combine to sell a ruse that will hopefully keep both of them alive long enough to escape Venda and the Komizar's brutal clutches. Along the way, the few stolen moments they share manage to deepen their relatively new romance into something far more mature.
Despite knowing from Dance of Thieves how this particular story would end, I still found the peak of this arc satisfying. I wish Pearson had dug in a little deeper at the pivotal moment, giving us a little more framework of the grief and anger inside Lia's mind, but I can appreciate brevity, too. The softball cliffhanger at the end was just my style, and I will eagerly start in on Beauty of Darkness tonight.