One of the classes that I am taking this semester is entitled "Strategic Prayer and Spiritual Warfare." As a result of this class, I am being convicted that my prayer life is not what it should be. In fact, I recently preached on this very topic. Part of that conviction has come as a result of three different books. I would highly recommend that you pick up all three and spend some time prayerfully going through them.
Prayer: The Timeless Secret of High-Impact Leaders by Dave Earley. There is much that I could recommend to you about this book, but it is better if I simply quote Dr. Ergun Caner: "Do NOT read this book if you want information. Read this book only if you desire a transformation. It will drive you to your knees."
The Necessity of Prayer by E.M. Bounds. This short little book packs a lot of punch. There is enough "food" here to keep a hungry pray-er fed for years. It is packed with Scripture and is conversational in tone. Well worth your time.
Quiet Talks on Prayer by S.D. Gordon. This book reminds me a great deal of Lectures to My Students by Charles Spurgeon. The format is that of a lecture transcript, but it is packed with nuggets that will convict and challenge you.
If you desire a stronger, more fervent prayer life, I can't recommend these books more highly. Of course, as Tim Challies wrote recently, "I want to be a prayer warrior, but I find that I'm more of a read-books-about-prayer warrior," we need to make sure we are putting what we read into practice.