A Mind for Missions: 10 Ways to Build Your World Vision Paul Borthwick (NavPress) The best and most basic book on the topic, packed with ideas, ways to begin to grow into a heart for missions and to learn more. Very readable and good.
God's Global Mosaic: What We Can Learn from Christians Around the World Paul Gordon Chandler (IVP) An absolutely delightful--and challenging--book showing what Western Christians can learn from believers in other continents. A healthy reminder that there are Christians elsewhere and that we've got much to learn.
Changing the Mind of Missions: Where Have We Gone Wrong? James Engel & William Dyrness (IVP) A highly regarded book which raises serious questions and calls for innovative thinking. Has gathered rave reviews from the heads of many large, evangelical mission agencies, insisting that the diagnoses is accurate and the recommendations right. Important.
The Gospel in a Pluralistic Society Leslie Newbegin (Eerdmans) One of the most important world Christian leaders in the past generation has given us a classic on the truth claims of Christ and how to speak them meaningfully in a pluralistic world.
Perhaps a bit serious for those not used to good theology, but this truly is essential reading, not just for the mission field but for any thoughtful and caring Christian.
Transforming Mission David J. Bosch (Orbis) Perhaps the most talked about seriously academic book on missiology of the past 25 years. Exceptionally important.