As the first book in a series of five on the Christian life, The Green Letters emphasizes both the doctrinal and experiential aspects of maturing in Christian living. The book is grounded in Scripture and enlivened by quotations from noted authors. "Not I, but Christ" is its theme. The author makes this arresting statement regarding the dynamics of the Christian life: "God . . . doesn't intend to help us live the Christian life. Immaturity considers the Lord Jesus a Helper. Maturity knows Him to be life itself."

Perhaps the greatest drama in the world is the slow and subtle growth of character in the Christian. Beauty of character can be developed only through years of reflection and experience in the Word of God as the life of Christ is increasingly lived by faith. The Christian life is a healthy, robust kind of life. It advances also through trials, for in one who has faith even suffering is not wasted, but becomes a means for increasing spiritual vigor and strength.