Somehow the author, as is often the case with self-help books, was never very good at any of the things they claim to teach. Personally I think it likely that the entire industry is a scam, but if someone has a link to a scientific study which says otherwise - I would be quite interested.

edit: > By 2006, research firm Marketdata estimated the "self-improvement" market in the U.S. as worth more than $9 billion (https://en.wikipedia.org/wiki/Self-help#The_market).