by John Piper
In this book, Piper presents an in-depth look at the Christian discipline of fasting. He lays out the history of fasting in scripture and explains why we should incorporate fasting in our lives today. Whereas Franklin's book was a general overview, A Hunger for God delves deeply into the subject, explaining how fasting is an effective way to glorify God and bring us into a closer relationship with Him.
While the why's of fasting are completely divulged, this is not a practical book for a how-to.
Fasting for Spiritual Breakthrough
by Elmer Towns
Here is the "how-to" of fasting! In Fasting for Spiritual Breakthrough, Towns gives a brief introduction stating a case for fasting then gets right to the point. He introduces nine basic fasts found in scripture and gives the purpose and some specific devotional ideas to guide you as you abstain from eating. His devotions include fasting for: freedom from addiction, to solve problems, for evangelism, to overcome fears, for wisdom in decision making, and more.
Both of these books use Isaiah 58 as a main text.