No reader should feel intimidated by Brendan O’Leary’s three-volume A Treatise on Northern Ireland. As accessible as it is erudite, it bears comparison with JJ Lee’s classic study of failure, Ireland, 1912-1985: Politics and Society (1989), which secured a wide readership. Here, the temporal span is longer – O’Leary, Lauder professor of political science at the University of Pennsylvania, peers back into the 16th century and predicts into the 2020s and beyond. And while the great failure of 1920-21, partition, gives the book its subject, it also concerns success – the Good Friday Agreement of 1998... Not all his arguments will win cheers from all nationalists. Reflecting on the Famine, which some but not all nationalists have represented as genocide, O’Leary finds no evidence for premeditated and intentional homicide of the genus, but argues that British governments after Peel might be open to a charge of “geno-slaughter”, a term derived from manslaughter-unpremeditated and unintentional killing. Especially valuable, as we approach its centenary, is his consideration of the division of Ireland in a comparative analysis of partition... Throughout the three volumes, the range of the political scientist’s reading, not only in his own discipline, but in Anthropology, Demography, Economics, and, especially, History, should bring a blush to the cheeks of many scholars who have written on Northern Ireland and, indeed, on the rest of the country. A Treatise is, in places, witty... More generally, A Treatise is written with a deep empathy for the people of a place shaped by long-term historical processes, which O’Leary elaborates, and appallingly short-sighted government, by both Unionists and the British, which he documents.