I have not read The Millionaire Next Door, but that seems fraught. Does it avoid survivorship bias? E.g. Playing the lottery is a 'habit' common to all lottery winners, but it's also common to all lottery losers, of whom there are many more. If you only studied the winners though, the lottery might start to look like a wise investment. Maybe the habits common to millionaires are counterproductive for the average person and only helpful to the lucky few.