"In reading Chesterton, as in reading MacDonald, I did not know what I was letting myself in for. A young man who wishes to remain a sound Atheist cannot be too careful of his reading. There are traps everywhere – ‘Bibles laid open, millions of surprises,’ as Herbert says, ‘fine nets and stratagems.’ God is, if I may say it, very unscrupulous." -C.S. Lewis In short, Lewis means to say that there is power in the Word of God. He is warning (or perhaps lightly mocking at) atheists because he knows that if they [i]read[/i] God's Word, things will happen and eyes will be opened. Better?