Initiates do not read many books written by human beings.
For them, the one true book is the Book of Living Nature; they constantly pore over this book, endeavouring to decipher the symbols, structures and forms presented within it.
And the Book of Living Nature is not simply an inventory of all the minerals, plants, insects and animals in the world. Indeed no, it contains the life of all creatures of all worlds.
It is not a matter of knowing the external aspects of nature, but the surge and flow of life itself and all the subtle correlations between the different planes of the universe.