The Screwtape Letters is one of my all-time favourite books. Lewis' mastery of irony works to great effect in persuading the reader to take a second look at themselves. At times stinging, frequently profound, this is a book unmatched by others and in a category all it's own. Advice from one devil to another? Pure genius.
Some favourite quotes:
IV
"They constantly forget... that they are animals and that whatever their bodies do affects their souls."
"Keep them watching their own minds and trying to produce
feelings there by the action of their own wills. When they mean to ask Him for charity, let them, instead, start trying to manufacture charitable feelings for themselves and not to notice that this is what they are doing. When they meant to pray for courage, let them really be trying to feel brave. When they say they are praying for forgiveness, let them be trying to feel forgiven."
{IV always make me reconsider my prayer habits...}
VI
"Do what you will, there is going to be some benevolence, as well as some malice, in your patient's soul. The great thing is to direct the malice to his immediate neighbours whom he meets every day and to thrust his benevolence out to the remote circumference, to people he does not know. The malice thus becomes wholly real and the benevolence largely imaginary."
VIII
"It is during such trough periods, much more than during the peak periods, that it is growing into the sort of creature He wants it to be... He wants them to learn to walk and must therefore take away His hand; and if only the will to walk is really there He is pleased even with their stumbles. Do not be deceived, Wormwood.
Our cause is never more in danger than when a human, no longer desiring, but still intending, to do our Enemy's will, looks round upon a universe from which every trace of Him seems to have vanished, and asks why he has been forsaken, and still obeys."