Books like this can be helpful, I guess. But not to me. I've already been down the complicated prayer road. I found it cumbersome and disappointing and I won't travel that way again.
Jesus taught the simplicity of prayer. We see this in the first few verses of Matthew 6. What he said boils down to three simple truths:
There's no right volume, tone of voice or vocabulary for prayer.
We don't need to be "somebody" in the religious world for God to answer our prayers.
No one has God's attention more than another. The Father wants us to speak to him honestly from our hearts. He's listening.
"Your Father who sees you in your secret place will reward you in public." Matt. 6:5