The New Atheism did not arrive as a single manifesto but as a run of bestsellers arriving in close succession. Sam Harris opened it with The End of Faith in 2004. Richard Dawkins followed with The God Delusion in 2006, the same year Daniel Dennett published Breaking the Spell. Christopher Hitchens closed the run with God Is Not Great in 2007. Commentators soon grouped the four authors together as the movement's Four Horsemen, a label all four eventually accepted.
Of the four, Dawkins's book reached the widest general audience and sold the most copies, helped by his existing reputation as a biologist and popular science writer rather than a philosopher or a professional critic of religion. That existing platform mattered: The God Delusion did not introduce Dawkins to readers, it redirected an audience that already trusted him on evolution toward a new subject, and much of the book's argument leans on that same scientific framing, treating a god's existence as a testable claim rather than a matter settled by faith or tradition.
The book's commercial run, several million copies and long stretches on bestseller lists across the English speaking world, gave the broader New Atheist current a level of public visibility none of the other three books quite matched on their own. Whatever the movement's later reputation, in 2006 it was, for a period, one of the most talked about developments in publishing on either side of the Atlantic.