This book is organized into 40 chapters, which I think corresponds to the 40 days of the temptation faced by Jesus. The book is especially good for new Christian. It told us that we can never gain real satisfaction and success if we don't look at God. It teaches us to be humble in front of God, and then be a servant and a friend of God. What it means by "purpose" in the book title is that we are living our lives to realized god's plan.
What it means by "purpose" in the book title is that we are living our lives to realized god's plan.