The obtuse academic language makes this pretty inaccessible. I think I've got the gist of her theory - turns out she wrote another book (Bodies That Matter) partially to clarify her abstractions. 

What I got from this: gender is the collection of actions we take to express ourselves, performing under the structures of power in our societies. Because this was foundational in queer theory, it's not an unknown perspective to me; this made it slightly easier to parse such a dense text.