Answer:
Three little letters. A paradox to some. The worse that it is, the better it becomes.
This is needed both for courage and hardcover books.
The barber of New York shave all men in New York. No man living in New York is allowed to shave himself. The barber of Nee York lives in New York. Who shaves the barber ?
Useful tool for who in darkness dwell. Within you, corrupting like a deadly spell.
What tree that definitely grows does not have a shadow and does not grow fruit?
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?