I am often pressed to recommend books that will teach a person "all about Tesla coils." I have only seen one that really impressed me and that was Duane Bylund's, Modern Tesla Coil Theory. I say this because of the excellent grounding one is given in the theory of resonance and transmission lines. It is not overly mathematical, but is long in "plain speak" and filled with examples. I recommend it to anyone as a good introduction to what resonance is all about.