A friend or fellow kibitzer may overrule the clerk who suggested the book. This is one of those situations where you hope common sense and logic override outside interference. You've got shooters who have won, but didn't know why. There are players who lost and can' t figure out how they gave it all back to the House. There are distraction, pressures, noise, and of course human nature among factors to deal with.
Sports bettors are quite diverse in their needs.
Some want shortcuts. At least the approach is honest. Some really want to take it all the way through from the basics to advanced concepts. They buy all the books which exist and accept it as a student taking a course in chemistry. We all approach a problem differently.