The premise of the book is to view the Christian life as books on a bookshelf (i.e., ministry, family, work, recreation, etc.), with all your books leaning on the stability of two bookends: The righteousness of Christ and the power of the Holy Spirit.
Within this book you will find a thorough explanation of the gospel. Then it goes on to describe three enemies of the gospel (and that right there, folks, is worth the price of admission). The three gospel enemies are self-righteousness, persistent guilt, and self-reliance. After explaining the concept of these enemies of the gospel, the authors give self-examination questions to allow you to explore these ideas in your own life.
It is a small book literally (in physical size and in page numbers-154), and I cannot think of a better discipleship tool for our present age. I highly encourage you to read it and consider using it in a study with a young Christian or in a book study at your church.