One evening in 2006, at a colleague's house, I met a friend of her teenage daughter. He was intellectually curious, and obviously bright - but implacably loyal to his parents' born again Christian faith. We spent pretty much the whole evening arguing with the poor boy, appealing to his logic and reason - all to no effect. There must, we despaired, be some seminal atheist text we could refer him to. We just couldn't think of one. But lo - ask, and ye shall receive. Not a month later, Richard Dawkins published The God Delusion, a scorching manifesto for secularism....