Serpent's Kiss picks up shortly after the close of Storm's Heart. Rune had bargained with Carling for Tiago's life and now has to pay the piper. He begins this book, by going about doing all the things that need to be done to set up for an extended leave of absence. To be honest, it was a bit boring. It's not till Rune actually makes it to Carling's island and the two start interacting that things pick up and get interesting.
Carling had come across in the previous book as a bit cruel, not intentionally, but due to withdrawing from the human race. Here we find out why. Her ailment is fascinating, and from the hints dropped, I was quickly postulating theories and scenarios as to what could happen. I did have some discomfort during some scenes that became pivotal to the story line continuity. I hate to be spoilery - but time travel and messing with events and personal histories squick me out a bit. I had to suspend belief a bit to make it work in my head, without making me grumpy.
Overall, I did enjoy the story. We got to see old friends, meet new creatures and fill in more of history of the world Ms. Harrison has created. This book didn't do it for me as much as the previous two, but it was still worth 3 stars.