Recommended books on prayer:
A Hunger for God: Desiring God Through Fasting and Praying by John Piper
Becoming a Woman of Prayer by Cynthia Heald (TLC study, Fall 2012)
Confessions of a Prayer Slacker by Diane Moody
Handle with Prayer: Unwrap the Source of God's Strength for Living by Charles Stanley
Praying Backwards: Transform Your Prayer Life by Beginning in Jesus' Name
by Bryan Chapell
Pray Big for Your Marriage: The Power of Praying God's Promises for Your Relationship
by Will Davis
Transforming Prayer: How Everything Changes When You Seek God's Face
by Daniel Henderson
Please feel free to suggest books of your own and/or comment on any of them.