I am only a half way through the book and can tell that it works. However, some things i wish were explained better, more detailed.
Jack Kornfield is a great editor-teacher. This is the best collection of Buddha's instructions for Zen Meditation or "Yoga for the Mind" I've come across. Read it slowly and carefully and see if it doesn't put you in a non-dualistic state.
"As you read the teachings in this book, remember that they are not meant to be philosophy, poetry, or spiritual studies for you to consider. They are words of truth that can bring you to awakening." - Jack Kornfield