The smell of old books is not only the ineffable scent of knowledge, but also an understandable perfume that emerges from various chemicals interacting as they age. And scientists are analyzing exactly what causes this nice, smart odor.
Vox reports that aging paper, binding, ink, and glue can emit scents evocative of vanilla and grass. A polymer found in paper called lignin degrades into vanillin, while 2-ethyl hexanol gives a slightly floral odor, and benzaldehyde has an almondlike smell. It's a great recipe for a custom scent that lets people know you are an adorable, seriously minded, floral-marzipan-smelling nerd.