David performs different versions of Any Card At Any Number--some of which are "The Berglas Effect" and some not. The methods vary depending upon whether he's onstage, closeup, working for one person or multiple people, the exact circumstance, and every other variable you can think of.
His methods are not some simple "secret" or "answer" that you can buy and go off and do the way you would a paddle trick or even a Center Tear.
There will be several methods in the book, but if you think that you can just read any of the methods and then run out and do them within a day, or even a few weeks, you're mistaken.
There is no gimmicked deck, no one secret, and everyone who reads the book starts with the disadvantage that they are not David Berglas.