When Sam Harris published his first book The End of Faith he was flooded with letters from Christians full of hatred and bigotry. This book is his reply to those hated comments and to those Christians who "...accept the divinity of Jesus Christ will experience salvation after death." & to those that believe if you do not follow Christianity as a whole you will be sent to hell. 
 Little background on my views: I myself am not religious nor atheist. I believe in a higher being of some sort but I'm not going to give it a name because I have no idea what it is. 
 Sam bashes many things in this letter from killing others who do not believe the same, the bible believing in slavery, and morality without the belief of God. I do believe that many people use religion as a means of excuse for harming others, but I do not believe that all religion is bad. More so I don't believe all religious people are bad people. Sam spoke of many already well known ways to dispute science vs. religion and all the negative aspects of religion. He fails to realize the good that has come from it though. A little too far fetched without encompassing the total imagine in my opinion.