Tim Keller's The Reason for God is this generation's Mere Christianity. It addresses the toughest questions non-believers and believers pose with an emphasis on dialogue, reason, and sound biblical teaching.
Each session offers a downloadable PDF and a downloadable MP4 video that can be purchased separately. You can also buy all the video sessions together, or a complete kit which includes all the video sessions plus group use PDF participant's guides. The group use PDF covers each of the video sessions and can be reproduced for all the members of your group.