How do you know that the professional is interested in helping you rather than regular money ?
Perhaps a cynical question, but perhaps one reason why the less expensive book route may be oft considered ? With everyone advertising to solve your problems, how do you decide who to trust ?
Well I'd agree to buy a book that is thorough in its science, but how do you really know its science is good enough? Same problem. Should I extensively read scientific literature on the subject, or should I just read books that are close to being mumbo jumbo, since it's aimed to be read by non scientists?
A psychiatrist is someone who had extensive education in psychology and medicine, who I can talk to. That's a little easier to sense things when you're face to face with somebody. It's much easier that way, just like it's easier to learn a complicated subject by asking questions instead of reading many books.
I guess you're right, I could read a book on the subject, but I'm a little skeptic...
Usual rule of thumb: let a professional, which holds enough scientific baggage, and a trained eye, help you for this. Psychology is already quite shallow as a science, so I wouldn't use a book.