R.C. Sproul is one of my favorite authors. His book The Holiness of God shaped my Christian life more than any other book that I have read besides the Bible. I own around 15 of his books, and the one downside to his books is that there is a lot of repetition from book to book. The Prayer of Lord breaks this mold and is one of his most original works, not to mention one of the best books on prayer that I have read.
The Prayer of the Lord focuses on how to pray in the same way that Jesus prays the Lord's prayer. The first chapter focuses on how we should not pray, which is very helpful. Following that, each chapter zooms in on a part of the Lord's Prayer and explains how we should apply the lessons to our own prayer life. For such a short prayer, it is a refreshingly rich book, and you will be blessed by reading it.
One chapter that I thought was particularly good was the "Give us this day our daily bread" chapter. Praying for daily provision is something that is easy to forget in our society. We tend to pray for security over the next 30 years, or pray only when we hit a rough patch. Praying daily for provision is humbling and it helps enable you to see how God is working in your life.
The book is excellent by itself, but it also includes an appendix on why we pray to a God that is in complete control. Many make the mistake of praying as if they are informing God of something that he did not already know in hopes of changing his mind. Many others mistakenly discount prayer as largely unnecessary - we can't change God's mind after all. Sproul expertly dismantles both of these views and presents a profound, Biblical view on prayer.
It would be a mistake to assume that this small book belongs in the gift book section or that it is "Theology Lite." It is an excellent treatise on prayer and a great read as well.