Some diagnoses and characteristics are more toxic in parents than other diagnoses---and narcissism in a parent is very hard on a child. It can express itself in a million ways. For example, the parent will go outside in the winter and put on their own jacket but not even think of the shivering child needing a jacket. The narcissist's children are like things to him/her---like decorations he/she might wear.
A major problem is that our society is geared towards producing narcissists. I recommend The Culture of Narcissism: American Life in an Age of Diminishing Expectations by Christopher Lasch (1991) to understand the societal causes of narcissism and how it expresses itself.
For advice on how to deal with a narcissist I recommend Malignant Self Love: Narcissism Revisited by Sam Vaknin and Lidija Rangelovska (2001). This book is neither entirely consistent nor reflective of scientific research, but it has some handy insights. For example, if you want to get rid of a narcissist, the message to convey to him/her is: "You bore me."
I believe a narcissist puts up a great fake front to cover his/her terrible, low self esteem. The self esteem gradually shrivels smaller and smaller---until it's like a tiny raisin. But a raisin covered up by a huge fake cover. The raisin is the private self. The fake front is the public self. These two are completely different. If someone hasn't lived with people who have one public self and a completely different private self, it's hard to believe they both exist in one person.
Unfortunately, manipulative and charming narcissists can slither into court or into the psychologist's office and bring them under their narcissistic spell. They're hell to live with, but in the 10 minutes when they face officialdom, nobody is sweeter or more appealing---men and women. These people can be dealt with in court, but one has fully to understand them.