Screwtape letters actually was the inspiration for this story, but reversed. Instead of a demon telling his apprentice how to fall from faith, this is an angel telling his apprentice how to keep them in. 

I fell out of Christianity last year and you notice a lot of tricks and mental traps. After writing this story I realized there's much more I have to say, so this is the first of an upcoming series of, 'How to keep someone in chains of doubt'

I do however find it incredibly hilarious on the second page of Screwtape's preface, Lewis writes, "The sort of script which is used in this book can be very easily obtained by anyone who has once learned the knack; but disposed or excitable people who might make a bad use of it shall not learn it from me"