This is one of the best books ever written, regarding the art of trading. The majority of trading books focus on technical aspects of trading. Douglas discusses the psychology of trading. The psychological aspect of trading is far more important, then the technical aspect.
Douglas outlines how controlling your emotions will allow you to make sound assessments, of various probabilities. Trading is never a black and white type of environment. You have to be clear headed at all times, and therefore be able to make good decisions. Douglas points out all the areas and mental traps, that prevent a person from making a good decision.
I will also warn, that you may have to read the book more then once. The first time I read this book, I thought it was a complete waste of time. Douglas`s book seemed more like Jimmy Hendrix acid trip, then something that would help a trader. I later found out this book is a gold mine of trading information.