You can never be too careful

Lewis in his Surprised by Joy talks of the years leading up to his conversion in 1931 and the ideas he was leaving himself open to:
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.
You are never so sure what God might use. Sometimes, though, I wonder if Christians forget that. I worry that we might become too careful of what we read. We're afraid to push the envelope and let God speak again and again. It's Scripture that remains the authoritative voice, but are there other voices that help amplify what's there?
A sound Christian can, perhaps, be too careful of what she reads.