In the compelling final volume of his magisterial trilogy, "A Treatise on Northern Ireland," Brendan O'Leary meticulously unravels the complex tapestry of political, social, and historical threads that culminated in the landmark Good Friday Agreement. With unparalleled expertise, O'Leary navigates through the labyrinth of negotiations, failures, and milestones that shaped the path to a peace long yearned for but often doubted. This narrative not only chronicles the arduous journey towards the agreement but also critically examines the seismic shifts it heralded for the political landscape of Ireland, both North and South. It stands as a testament to a moment when the future of Ireland's sovereignty and its relationship with Great Britain hinged on the will of its people, encapsulating a pivotal stride towards the full political decolonization of Ireland. Yet, O'Leary's analysis does not halt at the threshold of peace; it ventures into the tumultuous waters that followed, casting a scrutinizing eye on the aftermath and the unforeseen challenges that emerged. The narrative delves into the delicate balance of power-sharing, the evolving identities and allegiances within Northern Ireland, and the unforeseen repercussions wrought by the UK's referendum on EU membership. O'Leary's treatise is as much an examination of a historical milestone as it is a forward-looking inquiry into the fragility of peace in the face of political upheaval. With a keen analytical lens and a deft narrative touch, O'Leary offers a critical, comprehensive, and captivating account of Northern Ireland's ongoing journey through reconciliation, division, and the quest for lasting peace.