Contents Panel in EPUB books in inconvenient.

I just downloaded "Javascript Cookbook" in EPUB format.

I wanted to be able to quickly scan the contents of the book, but the left Contents panel is very inconvenient, as it extends for over 500 double-spaced lines, but cannot be hierarchically expanded or contracted.

Is there some way to add hierarchical expansion and contraction to that panel?

Alternatively, is there a way to set up an external html page with hyperlinks into the text of the book?