With great economy and elegance, one the greatest spiritual writers of the last century writes practically, simply, briefly and beautifully about prayer.
Prayer is not primarily something one does. Prayer is something that is. It is in God that we live and move and have our being. God is always in us, waiting to be released into expression.
All the different techniques and ways of prayer are reminders, alerting us that every moment of our life is lived in the presence of God. Prayer is a constant, it is like a marriage, not a flirtation carried out in a series of clandestine meetings.
I suppose I want books about prayer to be more inspiring than this, but the spirit did not move for me on this one. It's basic but it might be better for other people. Personally I would recommend the God of Surprises if you want to learn about prayer.