Wow, the book started with a bang and hardly stopped. Events happened quickly and there was a lot going on. Hunter pulled and brought together numerous threads and plot lines from earlier books. If you are new to the series, STOP, do not pass go, but grab book 1 and read in order. You can not jump into the middle of this series. 
 There was a scene with Alex and some vamps where my heart almost stopped and I was having very unkind thoughts about Ms. Hunter. Throughout the story, she put me through the wringer but overall I was happy with the book. I loved the blend of vamp politics, relationships, action, suspense, world building, even romance, and religion. There are revelations galore and I decided that I really need to go back and read the earlier books again, especially in light of the revelations. Also, my feelings on some characters, including Jane herself, have changed over the series. Hunter does not keep her characters, or her world, static but lets them grow and change. It's one of the strengths of the series. 
 "Cold Reign" kept me reading, flipping the pages on my ereader to see what would happen. It kept me guessing, made my heart race, and gave me all the feels. It's a smart, thrilling, complicated story that is exactly what urban fantasy should be.