I happened to read Locke's third novel ("Saving Rachel") first and enjoyed it, so I bought the first and second in the series. I enjoyed the first, but I though this second book in the series (reviewed here) was weak. My biggest disappointment was the absurd and unnecessary plot twist two-thirds of the way into the story. It seemed amateurish and poorly designed play on a stale vehicle to add some drama and evoke an emotional response from the reader. There seemed to be no justification for it and it spoiled what had been a good story. Perhaps the plot twist gains more legitimacy and relevance by coming into play in later books in the series? I don't know. I also found the "Little People" an odd choice.
I had been excited to discover this author and read two of his books ("Saving Rachel" and then "Lethal People") in quick succession before jumping into the third ("Lethal Experiment"), which I had to force myself to finish. I'm not sure if and when I'd dive into the fourth in the series.