Consensus is that he overestimates the # of BB/100 you can make reading tells, and that many pros have studied the book and will try to give false tells. I believe Feeney talks about tells in his book 'inside the poker mind' and says that many tells will be player/situational dependent and much more subtle. In addition, he says if you spend too much time trying to pick up tells, you can miss other important information.

Figure Caro's book as an intro on things to look for and then go from there.