42 atheist celebrities, comedians, scientists and writers give their funny and serious tips for enjoying the Christmas season.When the Atheist Bus Campaign was first launched, over £150,000, was raised in four days – enough to place the advert 'There's probably no God. Now stop worrying and enjoy your life' on 800 UK buses in January 2009. Now dozens of atheist writers, comedians and scientists are joining together to raise money for a very different cause.The Atheist's Guide to Christmas is a...