<p>With sales in the tens of millions the Left Behind books are the biggest selling inspirational series of all time. </p><p>Those who were left behind after the Rapture must now make a crucial decision. Each person must choose whether to receive the mark of the beast or die. Never has faith in God been more important for the group of believers called the Tribulation Force who now face danger on all sides. Valiantly they continue to urge new followers to accept Christ's love.