In the long run, the book is worthless.
In essence the only real purpose a book of card meanings serves is to the people who don't previously have access to information explaining a better way. By simply understanding the fact that Oracle cards or even most forms of fortune telling (those not particularly associated with a specific culture and with prior rules to using them) are extremely personal, you've no long any need for the booklet. It's really just to show you an idea of how the cards work. The actual practice goes much farther than what the books offer information on.