What do the odd symbols in the 3rd book of the 39 clues mean?

The symbols in a 39 clues book refers to some sort of code. There is usually a key. The key in book 3 can be found on the very first page of the book. Most codes start on the 39th page. This book does too. When you figure out the code go to the 39 clues website and there is a page on this site with all the books on it. There should also be a button on the page which you solve the puzzle in the book. Hope this helps!