The Walk of the Spirit-The Walk of Power by Pastor Dave Roberson. 
You can down load it or read it for free off his website www.daveroberson.org
Best book you will ever read on the baptism in the Holy Spirit and the benefits and power behind praying in tongues! 
Do yourself a huge favor and take the time to read this book…it will transform your life if you apply what you read! I promise! 