I found the book very insightful. However, I disagree with Dr. Stout's "black and white" characterization of sociopathy. She implies that 4% have no conscience whatsoever, whereas 96% have a "normal" conscience. I don't believe that this reflects reality. I think to categorize someone as having absolutely no conscience is not only inaccurate, it suggests that they are hopeless and should be "written off". The fact is, we don't even know what a conscience is, and we certainly can't prove that a significant segment of the population has absolutely no conscience.
I'm not arguing with the basic concepts of the book... I just think that it's extremely inaccurate to paint a picture that these people are all equally ice cold and hopeless.