It sounds very odd to me. We do use 'textbook' in certain phrases, but not to call someone a textbook of something. "This is a textbook case of ....." - meaning the example exactly fits the accepted description/expectation of something - the definitive example. If you want to say to someone that they know everything about a subject (as in perhaps, being the human equivalent of a textbook on the topic) then we might say something like ' you are the fount of all knowledge' or the fount of all wisdom - fount meaning the source, origin.

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.