The book is nothing more than what it is; a book about butterflies. You're quite sure there's no hidden code or secret key inside, not even one you're not able to detect. You mean, who would even go through the effort of making such a detailed report just to hide something, right?

In any case, you turn around and find the front door open. It's strange, you think. Seeing the outdoors, the trees and the grass. You were sure you'd never be getting out of here, and yet there is is, the open door.