Pendergast's latest adventure cuts closer to home for him than ever before when he realizes that his wife, dead for twelve years, was murdered. Pendergast came closer to despair and shock than we've ever witnessed, and I believe he was closer to becoming unhinged as well. In fact, I think he crossed some lines he hadn't crossed before. I found it fascinating to see these new sides of Pendergast. He continues to intrigue me as a character.
The side story on Constance was curious, but after a while it became clear it was setup for the following story (which I'm already reading!).