I look at it like a compliment. I believe it to mean you are GENUINE in what they referenced. So if someone said "You are the textbook of Honesty" ... I see that meaning I know and practice to the letter, Honesty ... and I am Genuine or Sincere about it.
It also can mean that you are very wise in a particular area. If they said "You are the textbook of enjoyment", that would mean to me that I am looked upon for guidance on the subject or that I just know how to find enjoyment, wherever I may be.
SImply, I see it as a compliment that I am well educated and sincere in whatever they referred to.