I read and used the early '80s edition, before the "behavioral" was added to it, and around a decade or so ago realized that learning and following it made further talking therapy essentially useless.
The theory behind the "cognitive" part of it, simply put, is that thinking bad, not to mention incorrect, thoughts about yourself makes you feel bad. Adjusting your mental filters and the like to reality can then make a very big difference.
(Not, in my case, a complete cure, I've got an inherited refractory depression that my doctors and I supposize is bipolar in nature, I just never go manic nor cycle all that much. Adding a SSRI to the mix significantly improves it.)
