This is by far the most disturbing book of the series. The violence was a little too much for me, and although I've ordered book 5, I'm not sure that I can read it right away. I need a moment to regroup. It's an excellent series for exploring what happens to our humanness in the face of such horror that I tend to forget that there are even zombies lurking in the background. I'm not sure where this series can go after book 4, but I guess I'm in this for the long haul.