Grief is a topic he approached during his own very intimate experience with it, recording his thoughts in a journal at points throughout the months following his wife's death. Lewis intended to put down a sort of map to allow people mourning losses to know what to expect. The result is at once an emotionally vulnerable and theologically sound examination of personal disillusionment and the character and intentions of God.
It is worth noting that Lewis wrote this book in 1956, himself a veteran of the second World War, among a generation not at all familiar with men revealing or discussing their emotional states. Perhaps that is the void in the human conversation that inspired Lewis to pen his own observations for publication on this very emotional subject. Being a highly educated and well-respected theologian already, he was particularly suited both to write the book and to be taken seriously by his peers.
A Grief Observed