The introduction explains the origin of the book in a statement by Henry Scougal: "The worth and excellency of a soul is to be measured by the object of its love."
Piper helps us to think about what God loves instead of always thinking about how He relates to us.
Chapter 1 is a fantastic meditation on the delight of God in His Son. When was the last time you heard a sermon or read a book about the love between the Father and the Son? The Father's happiness is first and foremost a happiness in the Son.
"The day is coming when I will have the capacity to delight in the Son the way the Father does. My fragile eyes will get the power to take in the glory of the Son shining in his full strength just the way the Father does. The pleasure God has in his Son will become my pleasure, and I will not be consumed, but enthralled forever" (p. 28).
There is also an audio book available (Listen while you drive!)