This is one of the best books out there on apologetics and the existence of God. This would be a great book to go through with unbelievers, spurring on difficult and honest questions. This is a must-read.
Grab the book here:
Get in here on: Amazon
From the publisher:
In Life Together, Dietrich Bonhoeffer, renowned Christian minister, professor, and author of The Cost of Discipleship recounts his unique fellowship in an underground seminary during the Nazi years in Germany. Giving practical advice on how life together in Christ can be sustained in families and groups, Life Together is bread for all who are hungry for the real life of Christian fellowship.