I have mixed feelings about this book. Kaleb was always an intriguing character and as the series developed his own book and place in the pantheon became inevitable. Nalini Singh does an excellent job of presenting him as a very hard, dangerous, and still appealing man. He is similar to Rafael in her Archangel series, but even darker. 
 The story line, which finally concludes the Psy-Changeling series is satisfactory. She had created a complex world in which there was no easy solution and she does not cheat in this conclusion,resolving it intelligently with honest complexity. 
 I believe my only reservation is her main female character, Sahara. 
 Sahara is charming and immensely likable but she is essentially one dimensional. And that is the problem. 
 She loves Kaleb, he loves her, we can believe in his obsession with Sahara and his devotion to her, but it does not make a book. I wish there had been less of Sahara and more interactions with the other characters which were much better written. I wanted real scenes between Kaleb, Hawke, Lucas and Judd. While some are included, they are almost incidental. More is made of the Arrows which worked well, but the ones with the Changeling alphas are perfunctory at best. 
 I suppose it is difficult to write a romance with more than one male lead at a time, but an actual discussion with Kaleb and Hawke, two very strong alpha personalities, would have been worth sacrificing another love scene or two. And for Kaleb and Sienna, the two most powerful Psys on the planet, to never encounter each other is a waste of a great opportunity.