Answer:
I am a type of cheese made backwards
I wiggle and cannot see; sometimes underground and sometimes on a tree. I really don't want to be on a hook and I become a person when combined with “book”.
My first is in fish but no in snail. My second is in rabbit but not in tail. My third is in up but not in down. My fourth is in tiara but not in crown. My fifth is in tree you plainly see. My whole a food for you and me.
Two bodies have I, though both joined in one. The more I stand still the faster I run. What am I?
I suck.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.