First, let me say that I loved Alison Gaylin's books "Hide Your Eyes" and "You Kill Me". While I would have liked to have seen John & Sam in another follow up I think that may be down the road. John was mentioned a couple times in this book, I'm not sure what that was about.
"Heartless" has a great plot. Five years ago Zoe Greene, a crime reporter, got into the mind of a serial killer. The killer called her and told her he was going to murder more women for her and he did. Zoe, ridden with guilt, took a job with a soap opera magazine. There she met charismatic star Warren Clark and embarked on a torrid affair. Four months later Warren left the show to go to his house in a small Mexico town asking Zoe to join him. Zoe, having quit her job because she wouldn't capitalize on her relationship with Warren, headed to Mexico and Warren. When she arrived she learned there had been several extremely brutal murders in this picturesque small town. Fearing Warren is a member of a cult that may be responsible she begins to investigate.
All good. The description of the town, customs and the bizarre events were detailed and fascinating. But I never felt the characters were fleshed out or that I really knew them. There was very little about their background or even what they looked like. I couldn't bring myself to care much about them and thought they were boring. I found myself rushing to get through the book and the very end was anti-climactic.
So, this is why I gave it a three. Hope Sam & John will be back!