Jack S. Levy and William R. Thompson’s “Causes of War” is an excellent
textbook, and the one Prof. Stephen Walt uses for his Origins of Modern War class. It covers a lot of the major and even minor interstate and intrastate theories in very rich detail.
textbooks are pricey, I can say that there’s a full .pdf version of this book somewhere on the internet that you can find with a clever google search.
Constructivism is less of a cat and more of an instagram filter.
What does that mean?
Well, it means what you make of it.