This book is a compilation of numerous papers by C S Lewis. While having some disagreements with one or two papers, the book is beyond value with its insights into ethics, and probably more accessible than The Abolition of Man.
Lewis has well made the case that if ethics is mere subjectivism, then there is no objective reason to bother with any other human being, and also that the only monotheism explaining why God is neither under Morality nor has prescribed an arbitrary moral system is trinitarianism: one eternal being of three eternal persons - the Eternal Society which has created humanity in its societal likeness (Imago Dei). Ie on the human level morality, relational Right & Wrong, is consonant with God's own relational structure. Lewis scotched the idea of a Christian Morality - morality is global, although different religions & philosophies each have, or have had, emphases.
When the UK & western Society is falling into moral collapse, rejecting the Dei and so undermining the Imago, the moral objectivism (de-ontological ethics) presented by Lewis is a lifeline of reasoning & sanity.