I've personally recommended this book to numerous people. Essentially, if you have some kind of problem now e.g. addiction, anxiety, anger, depression, resentment: then you can link it back to you some kind of dysfunction at childhood. Once you see the cause and effect and work through that then those problems will disappear. I've just started working through the book and have done a few of the courses and it's made me understand why I do the things I do. Pop pyschology this is not.
I cannot recommend this book enough, but you will probably not be able to fully understand yourself without some basic 1 on 1 or group therapy.