Several years ago, I read both The God Delusion, and God is Not Great, by Richard Dawkins and Christopher Hitchens respectively. At the time, I did not know that those two authors, because those books, were regarded as part of the Four Horsemen of the Apocalypse, otherwise known as the New Atheists (or Gnu Atheists, because it is different). The other two Horsemen are Sam Harris for The End of Failth, and Dan Dennett for Breaking the Spell.
Breaking the Spell is subtitled, "Religion as Natural Phenomenon." Basically, Dennett argues that religion is nothing more than a byproduct of the growth of human beings. Religion is really nothing more than a byproduct of cultural evolution rather than a supernatural force. The Breaking the Spell comes from the fact that, until recently, talking about how religion is false is taboo and that, out of respect for religion, we should not burst the faithful's bubble, or, break their spell.
Dennett is a philosopher, and I did find comprehension of many parts of the book to be tough going, but, if you take the time to really comprehend what you are reading, the arguments are clear and concise. He takes you through a journey of psychological, anthropological, and cultural research on what is religion, how it came to be, and how it continues to hold value for some many.
One of the many fascinating discussions in the book as to do with belief in God versus belief in the belief in God and how those differ and how important they are to hold of religion on so many.
If you are interested in understanding theories of how religion came to be and how it continues its grasp on billions of people, then you will want to read this book. Dennett is not afraid of asking questions that will make most people of faith quite squeamish to hear the answer to.