Most of the following books can be purchased at Amazon.com or Christianbooks.com

Becoming a Prayer Warrior: A Guide to Effective and Powerful Prayer by Elizabeth Alves

E.M. Bounds books on prayer:   
Power Through Prayer
Prayer and Praying Men
The Essentials of Prayer
The Necessity of Prayer
The Possibilities of Prayer
Purpose in Prayer 
The Weapon of Prayer

Mighty Prevailing Prayer by Wesley Duewel

Rees Howells Intercessor: The Story of a Life Lived for God by Norman Grubb

With Christ in the School of Prayer   by Andrew Murray

Shaping History Through Prayer and Fasting by Derek Prince
​
Revival Praying by Leonard Ravenhill

Healing Care, Healing Prayer: Helping the Broken Find Wholeness in Christ by Terry Wardle