Sam Harris does a remarkable job of expressing his point of view to the reader. I would highly recommend "The End of Faith" to anyone, atheist or theist. - For the Atheist looking for a book to give to a religious friend, I would suggest "Letter to a Christian Nation"; it is much shorter, allowing one to easily read it in a single day.
Sam Harris is a brilliant man who eloquently and passionately advocates his belief that civilization needs to cease its dependence on religious dogma. This is truly an excellent read, and I highly recommend his follow-up text, Letter to a Christian Nation, as well. I should warn you that he's not too kind to those who still hold on to their religious faiths; this book was definitely written for people who think like him.
While I am sympathetic to Sam Harris' arguments against religion; I must say that he has much maturing to do as an author before I can whole-heartedly recommend his works. If you are looking for an informative and well written argument for Darwinian evolution which, naturally, refutes the weak arguments of organized religion look to Richard Dawkins' "The God Delusion." Harris, unlike Dawkins, often sounds pedantic and intentionally inflammatory. I do not doubt Harris' intelligence nor do I find significant faults with his core arguments (though his doomsday prognostications and radical politics can be difficult to stomach). However, his flip style of dealing with religious doctrine only serves to alienate (by deliberately offending) those semi-religious adherents who may be inclined to listen to reasonable arguments against their faith. Hopefully Harris will continue to mature and produce influential works in the future, but for now his works seem to do more harm to the American secular movement than good.
This is a great book that explores the reasons why faith fails us and indeed causes us more harm than it's worth. We accept so many nonsensical beliefs because so many other people believe them. But under the calm, rational light of reason, these beliefs crack and crumble. We need to do this reasoning or these unhsubstantiated beliefs will continue to create more pain for the people of the world. Sam Harris has done us all a wonderful service by writing this provocative book.