Answer:
I save lives on the ground and in the air
I am good at concealing what's real and hide what's true. Sometimes I bring out the courage in you!
I am needed for most animals and hardcover books
I hold two meanings. With one I may be broken, with the other I hold on. What am I?
I am lighter than the material I am made of. You see parts of me but more of me is hidden underneath.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.