The 48 laws of power by Robert Greene has to be one of my favourite books of all times! For those of us who have not read it, I'll do a summary of the laws but two laws per day. Enjoy!
1) Never outshine the master
Always make those above you feel comfortably superior. In your desire to please or impress them, do not go too far in displaying your talents or you might accomplish the opposite. Inspire fear and insecurity. Make your master appear more brilliant than they are and you will attain the heights of power.
2) Never put too much trust in friends - learn how to use enemies
Be wary of friends - they will betray you more quickly, for they are easily aroused to envy. They also become spoiled and tyrannical. But hire a former enemy and he will be more loyal than a friend because he has more to prove. Infact, you have more to fear from friends than from enemies. If you have no more enemies, find a way to make them.