I was reading about hell in chapter 8, in my copy of C.S. Lewis' "The Problem of Pain", it also reminded me of his book on heaven and hell called "The Great Divorce", which I also highly recommend. Below are a few selections from chapter 8, that I found good. The whole chapter is worth reading, I think it would be extremely helpful for anyone wrestling with the whole subject. Many people, both Christian or non-Christian, have an honest aversion to the doctrine of hell and have never truly heard much scriptural or philosophical discussion on the subject, Lewis is a great place to start.
"Some will not be redeemed. There is no doctrine which I would more willingly remove from Christianity than this, if it lay in my power. But it has the full support of Scripture and specifically, of our Lord's own words; it has always been held by Christendom, and it has the support of reason."
"Our Lord speaks of Hell under three symbols: first, that of punishment ('everlasting punishment' Matthew 25:46); second, that of destruction ('fear Him who is able to destroy both body and soul in Hell' Matthew 10:28); and thirdly, that of privation, exclusion, or banishment into 'the darkness outside', as in the parables of the man without a wedding garment or of the wise and foolish virgins. The prevalent image of fire is significant because it combines the ideas of torment and destruction. Now it is quite certain that all these expressions are intended to suggest something unspeakably horrible, and any interpretation which does not face that fact is , I am afraid, out of the court from the beginning. But it is not necessary to concentrate on the images of torture to the exclusion of of those suggesting destruction and privation. What can that be whereof all three images are equally proper symbols? Destruction, we should naturally assume, means the unmaking , or cessation, of the destroyed. And people often talk as if the 'annihilation' of a soul were intrinsically possible. In all our experience, however, the destruction of one thing means the emergence of something else. Burn a log, and you have gases, heat and ash. To 'have been' a log means now being those three things. if souls can be destroyed, must there not be a state of 'having been' a human soul? And is not that, perhaps, the state which is equally well described as torment, destruction and privation? You will remember that in the parable, the saved go to a place prepared for them, while the damned go to a place never made for men at all. (Matt. 25:34,41).
"The demand that God should forgive such a man while he remains what he is, is based on a confusion between condoning and forgiving. to condone an evil is simply to ignore it, to treat it as if it were good. But forgiveness needs to be accepted as well as offered if it is to be complete; and a man who admits no guilt can accept no forgiveness."
From "The Problem of Pain"" chapter 8
You can also read his treatment of the subject of heaven and hell in his great little book, "The Great Divorce".