I'm searching for a book...

[OneHandFlapping]

...that was read to me and my class mates a long time ago. It involved a man who was having religious doubts, and his mentor who did his best to discredit each doubt in turn.

At least one of the two may have been a priest.

It's not much to go on, I know, but it had a seminal effect on my beliefs - just not the one that perhaps the scripture master would have expected.

Can anyone help?

The Case for Christ?

Might it be written by the same man who writes the dilbert cartoons?

Might it be written by the same man who writes the dilbert cartoons?

The Screwtape Letters, by CS Lewis.

My first good turn of 2014!

I thought of The Screwtape Letters, curlew, but, IIRC, that's about a devil writing to his nephew about how best to lead human beings into temptation, as it were (though obviously its intention is the exact opposite).

Not to say it's not the book the OP remembers, though. We were read bits of it in school quite regularly, too!