How are we to understand petitionary prayer? This is a key question for any thoughtful believer who desires to take both the Bible and experience seriously. Some believe God answers any prayer as long as the one praying has enough faith and/or persistence. Others conclude from experience that prayer is really for our benefit and has no impact on God's actions. According to David Crump, both views are extreme and potentially harmful.

While books that deal with prayer from a devotional or experiential perspective have their value, Knocking on Heaven's Door takes a different approach. Crump carefully studies every New Testament passage that has to do with petitionary prayer and draws conclusions that are both theological and pastoral to help us understand the great mystery of prayer.