Nothing in the book is required to play. It just contains laminated versions of all the character sheets so that it is easier to note changes to your hero (damage, gold, etc) with a dry or wet erase markers.
www.sundialgames.com/characters
That site contains all the character sheets you will find in the Hero Book Companion. Though, you will need to download each character separately. It also contains custom characters made from the Kickstarter.
However, it does not contain the bio pages. Those are in the Quest Calendar itself.