Holiness, as Sproul writes, is a difficult concept for humans to understand and define. It is best understood by experience or by story. Sproul does attempt to define it, but it is best truly understood by stories, anecdotes, and analogy.
To this end, most of the book is Sproul examining personal stories that demonstrate holiness, but more importantly, and more extensively, he looks at the Bible to show what Scripture has to say about holiness.
Early on he looks at the Lord's Prayer, and notes that when we say it we "...often confuse the words "hallowed be your name" with part of the address, as if the words were "hallowed is your name." In that case the words would merely be an ascription of praise to God. But that is not how Jesus said it. He uttered it as a petition, as the first petition. We should be praying that God's name be hallowed, that God be regarded as holy."
Yes, the Lord's name is holy, but the prayer is primarily a petition that God's name be treated as holy. This emphasis is significant in that it sets the whole tone of the book. The holiness of God is not something to be taken lightly or irreverently. As Sproul later shows, God is holy and his holiness is a consuming fire. Even Moses was too unholy to see more than the back of God through the crack of a rock. This is a shocking thing, when one ponders it.
Some of the most helpful parts of the book are Sproul's examination of the deaths of Nahab, Abihu, and Uzza. They all died because they broke the law of God in rebellious, public ways. God struck Nahab and Abihu dead for offering "strange fire." Sproul shows the true rebellious nature of their sin. He also shows the casual nature the ark of God was treated by Uzza and his throng as they transported it. Uzza's touching it was the culmination of a heinous sin, not a simple slip of his hand.
It is one thing to be shocked by these stories, but another to stands as God's judge because of them. These are shocking things because God is holy and we are not. We rarely understand the meaning of this. We must bow the knee and worship, not place ourselves as the judge of God's actions or character.
Another very helpful passage was Sproul's treatment of the Rich Young Ruler who claims to have kept all the laws of God. Jesus tells him to "go and sell all you possess and give to the poor, and you will have treasure in heaven; and come, follow Me."
As Sproul notes, this is a frequently misunderstood passage. Many use it as an example to show that we should "get rid of all private property." Many others show rather, that the Rich Young Ruler is unwilling to give up an idol--his riches. This is true, but Sproul helpfully frames this in the context of the Ten Commandments. He writes:
"If we speculate and try to get into the secret recesses of Jesus' mind, we can imagine a thought process that went something like this: Oh, you have kept all the commandments since you were a child. Well, let's see. What is the first commandment? Oh, yes, "You shall have no other gods before me. " Let's see how you do with that one. Jesus put him to the test. If anything in the rich man's life came before God, it was his money. Jesus set the challenge precisely at this point, at the point of the man's obedience to commandment number one: "Go, sell all that you have...." What did the man do? How did he handle his only blemish? He walked away sorrowfully, for he had great possessions. The man was put to the test of the Ten Commandments, and he flunked out after the first question. The point of this narrative is not to lay down a law that a Christian must get rid of all private property. The point is for us to understand what obedience is and what goodness actually requires. Jesus called the man's bluff, and the man folded."
I suppose this is not a radical insight, but it is one that I'd missed in my reading. This is the kind of thing found throughout the book. I highly recommend it--particularly to young readers, as it is not a difficult to understand book, but it is often difficult to read as it puts man in his place.