The cover is awesome, in fact all of the art is. I loved the use of colors both in images and in the text, it really suits the adventure's theme.
You might consider making the "Boss Fight" and "The Chase" section headings match the colors you used for them in the Table of Contents and the font/style of the other adventure headings. Clickable links in the Table of Contents would be a nice touch too.
I really like that you presented 4 branching "adventures" - you managed to fit a lot of useful content in just a few pages. It is a lot to keep track of but there's a lot of depth and you provided several interesting ideas.
Reducing the page margins and increasing the margins between the columns of texts might improve legibility, there were a few places my eyes just wanted to keep reading from one side straight through to the other (like page 10).