Reddit reviews Depression: Causes and Treatment, 2nd Edition

Because they aren't legit. You are most likely reading pseudoscience.

Don't google self-help books. Depression isn't something you usually self-help. It's something you get professional help with, it's a fairly complex mental disorder, it's not something that a stranger can help you cure through a book.

If you want serious books on it, look at medical psychiatric textbooks only. If you want to learn more about treatments rather than about depression, look at psychiatric/psychologist guides (Official ones released my journal of medicine blablabla)

I haven't checked these at all but some less official ones I quickly found were:

http://www.amazon.com/Depression-Treatment-Aaron-T-Beck/dp/0812219643

http://www.amazon.com/Manic-Depressive-Illness-Disorders-Recurrent-Depression/dp/0195135792

Or rather check a book like this, there should be chapters on depression: http://www.amazon.com/Psychology-11th-David-G-Myers/dp/1464140812

Depression: Causes and Treatment, 2nd Edition