The Stranger You Know centers on FI team leader Casey Woods. A serial killer is targeting college-aged redheaded women, and taunting Casey with his kills. He soon reveals that she is more than just an investigator who has happened to catch the offender's attention; she is his ultimate target.
Kane crafted a good story here, and I particularly enjoyed the glimpses into the victims' lives. On the whole, though, I thought the characterizations were very lacking. I read reviews from a few others who had never read the other FI books, and they didn't seem to feel a connection to the characters at all. I don't remember feeling this way as much in The Line Between Here and Gone. I also appreciated that the earlier book focused on outside characters, while The Stranger You Know is almost entirely focused on the Forensic Instincts team. Those characters were just too stereotypical and underdeveloped to carry the story well, in my opinion.
Stranger is a fast-paced novel, though, great for weekend reading. The plot moves along well, and there were twists that I enjoyed, even if the were foreseeable. As a person with a connection to law enforcement, I took major beef with Casey's actions toward the end (no spoilers; I will leave it at that). There is a difference in being singularly focused on catching your criminal and being incredibly stupid, and Casey landed on the stupid side of that equation in this book (which is a shame, because I thought pretty highly of her in the previous book).
If it sounds like I'm being negative, I'm really not. Again, this is a good book to fly through in just a couple of days, because despite the character-based flaws, the plot will probably keep you sucked in. The thriller element is not lacking at all, and you may even find yourself staying up past midnight to see if all your suspicions were correct. I did.