Buss explains lucidly why we are (potential) murderers - there is good evolutionary sense in it! The instinct to murder resides in all of us. Ever thought you'd like to kill your wife? According to Buss you wouldn't be the first, perfectly normal middle class man to do it!
Stepfathers murder because they want to make room for their own off spring. Mothers murder their own children for freedom of finding another partner. Just don't mention the war....
Fortunately, there are also counter instincts in place that keep us in balance. What today is prison (and death penalty in some countries) was a risk in paleontological societies as well. Maybe not a prison, but humans definitely do make a cost-benefit analysis for planed murder.
Very good read and not too complicated for evolutionary psychology.