The author, Mike Caro is a very colorful person to say the least. He is referred to as the "Mad Genius" in poker circles and is an expert authority on the mathmatics and the human factor of the game.Poker tells are the biggest vice of any poker player, if you can use the tells of others to you're advantage and eliminate yours then you can easily come away with a few extra bets that would have left your stack. With control over your own tells, you can harness the power to confuse opponents in to not really knowing if they are getting a real one out of you or not.This book is the best and most extensive choice on the subject of poker tells. Many other books touch on the subject, but this is the one that will help out the most.