Answer:
A nut cracker up in a tree.
Come up and let us go. Go down and here we stay.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.
Turn us on our backs and open up our stomachs you will be the wisest of men though at start a lummox.
Its title means book.
What is so fragile that saying its name breaks it?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?