This might sound odd for those who know it, but the "48 Laws of Power" I've always felt worth recommending. It gives insight into how the power-hungry think and act, and is a valuable tool for helping to recognizing when a sociopathic/narcissistic person is trying to manipulate or undermine you. I think it crumbled away some of that social naivety I used to have, but in a good way. It made me more empathetic to people who's motives I previously would have failed to understand, and think more clearly about how I approach situations with people who don't have my best interests at heart. In short, it's a great book for making you think deeper and come up with solutions in the social realm.

Interestingly enough, I recommended it to a few friends of mine who quite clearly to me had toxic partners. In both instances, they thanked me for the book recommendation and took action to remove those people from their lives. Especially in relationships, it's good to have a frame of reference to tell whether someone truly has your best interest at heart, or they just want power over you and use your good nature to get that.

Keep in mind that the book is written in such a way to sound like your getting an education in politics from a full-blown psychopath, but once you get past that there's a lot of worth to be found.