FREE BOOK: TheWalk of the Spirit - The Walk of Power
http://amzn.to/1fBSssV [Kindle version: $.99]
http://bit.ly/1hyEyY5 [PDF version: Free; slow download]
http://bit.ly/1ldRqIK [Free pdf’s in 8 languages; slow]
Right now there is only one book available by Dave Roberson, but it is a book used by God to transform believers' lives in extraordinary ways.
If you want your life to change, or if you just want to increase your understanding about this phenomenon of praying in tongues, read "The Walk of the Spirit - The Walk of Power."
I recommend this book if you are serious about wanting a closer/deeper relationship with the Godhead. The theology presented lines up with the Scriptures. This is the best book I've encountered which explains the differences in praying in tongues for personal edification vs. the gift of tongues, etc.
I have read this book numerous times, gleaning additional insight with each reading. The gift of our prayer language is misunderstood. Most Christians do not realize the importance of utilizing what God has so freely given to those who ASK. Simply written, it is the truth of God's Word unveiled for those who will believe God's Word in spite of man's teaching.