How do religions die? Generally they don't, which probably explains why there's so little literature on the subject. Zoroastrianism, for instance, lost many of its sacred texts when Alexander sacked Persepolis in 330 B.C., and most Zoroastrians converted to Islam over 1,000 years ago. Yet today old Zoroaster still counts as many as 210,000 followers, including 11,000 in the U.S. Christopher Hitchens might say you can't kill what wasn't there to begin with.

Still, Zeus and Apollo are no longer with us, and neither are Odin...