If you think you know. If you think you have the answers read this book and have a taste of your ignorance.
I've read a lot of C.S. Lewis's work. No really. I've read his autobiography, collections of his essays (some manuscripts that were missing pages), his fiction, and many of his non-fiction works. His non-fiction is methodical, clear, and striking. He clearly shows why he believes what he does in those works.
But this work is different. This work was written after he had made those eloquent and cogent defenses of his faith. This work is the story of how his faith is all but destroyed, intellectual arguments notwithstanding. These are his journal entries after losing his wife, a loss I cannot fully comprehend. And in completely honest words he bares his soul. He feels the inadequacy of the intellectual answers. He mourns and questions in utter agony.
If you feel abandoned by God, read this book to commune with a fellow sufferer. If you feel you know the answers and your faith is unshakable, read this and see one of the great minds of the last century shook to his core. There are no easy answers here. And this heartrending account is well worth the read.