How is the smell in the library unlike the air anywhere else?

In Chapter 7, Bud walks into the library and comments that the smell in the library is not like the air anywhere else. He says that the air in the library is always cooler than the air outside and compares it to walking into a cellar in the middle of the July. Bud also mentions that the air smells differently than the air anywhere else. He says that if you close your eyes and take a big whiff, you will get confused as to what you are smelling because the smells of the books have blended together throughout the years. As soon as he enters the library, he closes his eyes and takes a deep breath. Bud mentions that he smells the old leather from the books, as well as the cloth covering them and the soft, powdery paper inside. Bud believes that the smells in the library have a hypnotic effect on people which is why so many individuals always fall asleep in the library.