Re: It is quiet in the library.
I suppose you could argue that a library itself can't be quiet. It can't be loud either. It's a room, a building, an inanimate object. It's the people in it which makes the environment either quiet or noisy. However, I certainly wouldn't consider "The library is quiet" as an incorrect sentence. No-one would question it if you said "The house was quiet" meaning "There was no sound emanating from the house".
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.