1) William Marshal : court, career, and chivalry in the Angevin Empire, by David Crouch
William Marshall (1147-1219) was not in at the start of British rule in Ireland, but he came fairly close: in 1189 he married Isabella de Clare, the daughter of Richard "Strongbow" Earl of Pembroke and grand-daughter of Dermot MacMurrough, the last Gaelic King of Leinster; the last thirty years of his life were spent balancing the demands of running a huge Irish inheritance which he had never expected along with the high politics of the courts of Richard I and King John, a story which ended with him being appointed regent of both England and Ireland after John's unexpected death. While not a lot of Crouch's book is about Ireland per se, the increasing entanglement of both the Plantagenet dynasty and William Marshal himself with the island is an important element of the story.
2) The Stolen Village: Baltimore and the Barbary Pirates, by Des Ekin
Today is a day when Ireland is particularly celebrated in the English-speaking world, but there are connections with other places as well, including North Africa. In 1631 almost the entire population of Baltimore in County Cork was kidnapped in a pirate raid and sold into slavery in Algiers. The book is a wee bit journalistic, but entertaining and informative, and explains why, when the possibility of ransom came up fifteen years later, only two of the abductees opted to return. The North Atlantic was a vast network of commerce in goods and people, the pirate chief in question eventually retiring to New Amsterdam, where some of his descendants are very well known indeed.
3) Early Belfast: The Origins and Growth of an Ulster Town to 1750, by Raymond Gillespie
This list reflects my own obsessions, but I think this very short history of the origins of my place of birth has a lot going for it. Belfast was founded not long before New Amsterdam/New York, and the populations of the two were more or less level pegging for the first few decades, though Belfast suffered more from internal and external conflict, which must have hampered growth, and New York's natural hinterland is, er, a little bigger than Belfast's. I learned from this that the story I had been taught at school about the town's origins around High Street was completely wrong; the axis of the medieval settlement was a block to the south along what is now Anne Street, and the seventeenth-century town was concentrated a block to the north around Waring Street. Only 180 pages.
4) Easter 1916: The Irish Rebellion, by Charles Townshend
A superb analysis of one of the turning points of Irish history, the week in April 1916 when the centre of Dublin (and, as Townshend reminds us, a few other places around the island) were briefly held by rebels before they were shelled into submission and their leaders executed. I learned a lot from it - the British had almost no intelligence capacity in Ireland before the rebellion; even the Pope had been told about it in advance, but Her Majesty's Government was caught completely by surprise. Townshend also dissects the (lack of) military strategy which informed the planning of the rebellion and situated the whole affair in the context of the Irish politics of the first decade and a half of the twentieth century.
5) Report of the The Bloody Sunday Inquiry, by The Rt Hon The Lord Saville of Newdigate (Chairman), The Hon Willian Hoyt OC and The Hon John Toohey AC
I read all ten volumes of this soon after it was published two years ago (see my notes on volumes I, II, III, IV, V, VI, VII, VIII, IX and X) and came away feeling that the costs and effort involved were very much worth while. If Easter 1916 was a turning point at the start of the twentieth century, 30 January 1972 was a turning point in the Troubles; the use of deadly violence against unarmed civilians on such a scale by state forces, and the state's failure to account for its actions, handed political momentum to exponents of armed struggle in a way which until then might just have been avoidable. It took 28 years but the truth was eventually established, in enormous detail, by the Inquiry, and while there is still room for disagreement with the report's findings, at least we now have a view of the facts which is unlikely ever to be surpassed.
And three extra:
Church and State in Modern Ireland, 1923-1979 by John Henry Whyte - the book that established my father's reputation, still a very readable account of Irish politics in general (not just church-state relations) in the middle decades of the twentieth century.
Interpreting Northern Ireland by John Henry Whyte - finished just before he died in 1990, but supplied an important analytical framework to understand what was going on during the Troubles, whose influence reached pretty far.
Science, Colonialism, and Ireland by Nicholas Whyte - all you could possibly ever want to know about the history of science in Ireland between 1890 and 1930.