This book argues that unforgiveness can be a morally appropriate response to grave wrongs when justice is not served. Jennifer M.S. Ang challenges the prevailing emphasis on forgiveness by presenting a case for unforgiveness as a necessary moral stance against unremorseful wrongdoers and perpetrators of absolute evil. The book explores three facets of forgiveness: the release of resentment, the restoration of moral relationships, and the acceptance of the past. Ang critically examines these concepts through the lens of historical atrocities, including the Nanking massacre, the Japanese military comfort women system, and the Khmer Rouge genocide, while also re-evaluating the Holocaust as a paradigm of absolute evil.

The book presents a nuanced philosophical argument that challenges conventional wisdom on forgiveness, particularly in contexts of extreme suffering and injustice. By drawing on historical examples of mass atrocities, it aims to provide a framework for understanding when unforgiveness is not only permissible but morally required. The work is likely to appeal to scholars and readers interested in ethics, transitional justice, and the philosophy of history, offering a counterpoint to dominant narratives that prioritize reconciliation above all else.