The real challenge is in getting them to recognize that their faith in the truth of that statement is actually dishonesty, since we can never prove whether it's true or false. Supplying an answer to an unanswerable question is an act of dishonesty.
The real beauty and mystery is in the simple existence of the question "what happened before?" But it's a question that they will never let stand unanswered.
Generally, anything by Dawkins is good, and highly scientific. The primary origin of most of my concepts posed here come from, as you might expect, "The God Delusion". This book is much less focused on science, more focused on history, but equally brilliant.
For a more biting criticism of religion, check out Christopher Hitchen's "God is not great: how religion poisons everything." Personally, I preferred this one. It's basically atheism with balls.