A few additional observations: Mental illness and stupidity aren't the same thing. Persons with NPD are often highly intelligent and hold important jobs. They don't respond well to counseling since they see nothing wrong with themselves, and they are frequently smart enough to fool even the best of counselors into thinking they are completely normal. I once had that happen to the extent that a couples counselor (a woman) pegged me as a chronic complainer and actually began flirting with my narcissistic mate!
In the narcissist's view, it's always the other person who is wrong or at fault. They will often twist the facts, project, gaslight, throw a tantrum -- whatever is necessary -- in order to avoid taking responsibility for their actions and to uphold their lofty opinion of themselves, even though such arguments can appear far-fetched and childishly ridiculous to the observer. This sort of behavior, however, is invariably reserved for spouses and close family members. Persons with NPD are very careful to "maintain appearances" in front of others.
Be careful who you confide in, as it can easily backfire and you will look like the crazy one. The only person with whom I can discuss the narcissist in my life is a friend whose father was a narcissist. Extended family members didn't believe me when I cautiously broached the subject because he is always on his best behavior around them. They think he's really a nice guy and that I'm too sensitive. They never see the person I see.