Green’s Dictionary of Slang

Book, the n.

(US black) the oral tradition that forms the basis of black pimping.

[US]‘Iceberg Slim’ Pimp 153: It’s a violation of the pimp book to quit a whore.
[US]Milner & Milner Black Players 39: Working from a book should not be confused with The Book which refers to an oral tradition containing the rules and techniques of the pussy game. Pimpin’ by The Book means following closely the traditions and techniques which have been transmitted orally until a few years ago when they were recorded for the first time in 1967 by Iceberg Slim, the pseudonymous author of Pimp: The Story of My Life.
[US](con. 1970s) G. Pelecanos King Suckerman (1998) 77: That there’s the Book. The Bible of the Street.
[US]F.X. Toole Pound for Pound 235: Bark be workin by the book, man [...] the pimp book.