As with the first 2 in the trilogy, this is a very well crafted, gripping mystery. And 'mystery' is the right word for this book, for unlike the previous 2, where you know who the key villains are well before the finish, this is not revealed in 'swan song' until close to the end. So of the 3, this is much more of a 'whodunnit'. Looking back, this is one of the features of the trilogy - each is a different type of thriller, yet all enjoy the great dialogue, complications, speculation, uncertainties, red herrings and well-hidden clues.
Would be great to have 3 more, but it doesn't look like it's going to happen.