I finished it along time ago, loved it, and have not had time since to sit down and blog on it, until now.
The storyline is fairly simple, and probably pretty well know, a series of letters from an elderly and experienced devil, Screwtape, to his nephew, Wormwood, during the period of the latters first attempt at temptation. Lewis uses this rather unusual basis to produce an absolutely brilliant book. Below is one of my favorite quotes:
He (God) is prepared to do a little overriding at the beginning. He will set that off with communications of His presence which, though faint, seem great to them, with emotional sweetness, and easy conquest over temptation. But He never allows this state of affairs to last long. Sooner or later He withdraws, if not in fact, at least from their conscious experience, all those supports and incentives. He leaves the creature to stand up on it's own legs- to carry out from the will alone duties which have lost all relish. 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. Hence the prayers offered in such a state of dryness are those which please Him best. We can drag our patients along by continual tempting, because we design them only for the table, and the more their will is interfered with the better. He cannot "tempt" to virtue as we can to vice. 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 decieved 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 roundupon a universe from which every trace of Him seems to have vanished, and asks why he has been forsaken, and still obeys.