He goes a little too far with the 'peacocking', but you do need to have something to talk about when you first meet someone you have never talked to before. And it is easier for the girl to ask you something about what you are wearing than some personal question. Girls tend not to talk to the average plain desperate guy, so you might have to work on yourself, your social skills, or your personality to become more attractive to girls. And it is even better if you can get the girl to come and talk to you first. That way there is less fear of rejection. Especially if you have the social skills to figure out if she is interested in you without being upfront about it right away.
The movie Office Space is a good example of these techniques used in a more normal real world type of setting, rather than at bars and parties. 'Peacocking' (I hate that word),doesn't have to be a piece of clothing but there has to be something that two people an talk about to get more comfortable with each other.
I haven't read the book yet, but I bet what is common sense to half the guys about flirting and relationships are totally foreign to the other half. The guys that had something unique about them in school growing up (on a sports team, had lots of friends, had a cool car, threw parties, or more money) would have a easier time starting a conversation with girls than the normal guy that would only be able to talk about school and the weather initially. Then the normal guy's self esteem and confidence goes down, and they don't learn anything about interacting with girls.
So while this guy Mystery might over do it for shock value and to get publicity, he does make some good points on what the successful behavior males use in real life.