It is about understanding what has affected one's heart and prevented God's spirit and God's words from changing the believer.
The Bible often writes about the heart, stating in many verses that human life comes from the heart. In the book of proverbs, the reader is told, "Guard your heart with all diligence for out of it comes the issues of life." In addition, Scripture often uses the idea of the fallow ground as a symbol of the heart, and seeds as God's word in the heart. The parable of the Sower in the New Testament is one such example, and the parable in Isaiah 28:23-29
However, legalism as well as humanity's fear of God and habit of trusting its own righteousness has affected the power of God's words and God's grace. This book is a manual on how to recognize and allow God to remove the images and emotional pains that have affected one's heart. In so doing, the seed of God's word is enabled to move freely in one's life.
This is not a new teaching but it is an indepth one that needs to be taught in every generation in the language of all generations. Many theologians --for instance the 19th century pastor William Griffith Thomas in his book, The Prayers of St Paul-- have spoken about loving God, accepting God's righteousness, and about faith in the heart. I feel the need to mention this because many Christians will assume this is a new-fangled teaching and sometimes one has to show that a teaching has been around for a long time and is truly Scriptural.
Although this book is clear and Biblical, it is a book that has to be read rather than described because many Christians will hear certain words and immediately think they understand the book. This is a book that truly describes the gospel.