This was, in my opinion, a very satisfactory supplement after reading Mere Christianity by the same author. I would however advise that readers follow my same order when reading the two, especially non-Christians, for the sake of helpful (although certainly not absolutely necessary) background. As always with Lewis however, the readership can be as diverse or secular as you please, and they still would no doubt appreciate this as a work of satisfyingly thorough philosophy if not also divine meditation on a very human level of humility.
The last couple of chapters, in which Lewis deals specifically with "pain" (and "animal pain") are far less compelling than the opening chapters in which he establishes the fundamentals of natural law and moral order. This is a brilliant line of reasoning, similar to the argument early in Mere Christianity, but better articulated here, I think.
The Problem of Pain ranks in the Top ten percent of non-fiction
C.S. Lewis's book, Miracles, is similar in scope and dimension to the Problem of Pain.
While I was listening, Vance did so well I often thought I was listening to Lewis.
The Problem with Pain no Problem
Christians will appreciate Lewis's apologetic approach the most.
Christianity is often questioned about how, if God is good, can we live in a universe of pain. It's a difficult problem to answer, but Lewis gives some interesting insight and thoughts on this question.
His arguments may not be correct, but do give reasonable thoughts with which to approach the problem and try to gain some understanding in the universe. It's worth considering for anyone interested in this problem of pain.