I have "The Expert at the Card Table" by SW Erdnase. I did some background checking ... I have heard rumor that the sleights demonstrated in this book aren't the best out there and can be seen by spectators when being performed. I also heard they weren't the ones he ever used.
What you heard doesn't ring true. Much of modern card magic is based on Erndase as a foundation. If you look at virtually any of the recent masters of card conjuring (like Vernon, Jennings, Giobbi, Hugard, Tamariz, etc.) they all refer to Erdnase and most have developed tricks based on Ernase's work. Even Jay Sankey uses the Erdnase Color Change extensively. I never knew that his name was Andrews spelled backwards. Several (if not all) of the writers of early card sleight of hand were absolute card cheats!