Best line I heard from a dog trainer about dog training books was, "What level does your dog read at?" His point was that if you read the book they all will get you to where you are going. They just get there differently. And a dog will only learn so much and then it comes down to breeding. No book ever gave a dog a good nose or even the desire to use it. They just point the trainer in the direction to get the most out of the dogs.