Oliver MacDonagh described the first edition of "Ireland: The Union and its Aftermath", published in 1968, as "a very small book with very large themes". The book rapidly reached the status of a classic and remains a thought-provoking survey of the history of Ireland from the Act of Union of 1800 until modern times. It has been unavailable for a long time. MacDonagh regarded the Act of Union as the most important single factor in shaping Ireland as a nation in the modern world. Although subordination to Britain had influenced Irish development before 1800, it took a rapidly different form under the Act of Union: "The experience of being assimilated by, and resisting assimilation into, a powerful and alien empire - perhaps the master-culture of the 19th century - was truly traumatic." For the second edition, published in 1977, which is reprinted here with a new introduction by W. J. Mc Cormack, MacDonagh included a chapter on the period 1968-73, taking account of the early years of the troubles in Northern Ireland.