I just read Lewis' Mere Christianity again, and now can't figure out why I'd waited so long to do so.
However, a quick caution: Lewis, while brilliant and very pleasant to read, is not entirely "within the ilk" of orthodox theology. It doesn't come out often, but there will be points at which you really should disagree. However, as Wilson said, even when Lewis is wrong, he is more enjoyable than most are when they're right.
A few quotes:
"...we know that if there does exist an absolute goodness it must hate most of what we do. This is the terrible fix we are in. If the universe is not governed by an absolute goodness, then all our efforts are in the long run hopeless. But if it is, then we are making ourselves enemies to that goodness every day, and are not in the least likely to do any better tomorrow, and so our case is hopeless again. We cannot do without it, and we cannot do with it. God is the only comfort, He is also the supreme terror: the thing we most need and the thing we most want to hide from. He is our only possible ally, and we have made ourselves His enemies. Some people talk as if meeting the gaze of absolute goodness would be fun. They need to think again. They are still only playing with religion. Goodness is either the great safety or the great danger--according to the way you react to it. And we have reacted the wrong way."
"There is a difficulty about disagreeing with God. He is the from which all your reasoning power comes: you could not be right and He wrong any more than a stream can rise higher than its own source. When you are arguing against Him you are arguing against the very power that makes you able to argue at all: it is like cutting off the branch you are sitting on."
There are far too many for me to type them all. It is a glorious, five star book that should be read with one eye on it and the other on the Scriptures.