I found the first essay, by Edwards, much the most interesting for my own selfish purposes; he finds that political violence escalated during the sixteenth century because the English government increasingly used it as a political tool; he challenges the received wisdom that the endemic violence of the system before roughly the 1540s was as serious as it subsequently became, and also points out that violence of the earlier period hit the topmost echelons of society particularly hard - he has a nice table breaking down deaths of Irish rulers as to whether they took place in peacetime, or at the hands of their own kin, or at the hands of others. The change then comes with the removal of Butler supremacy in the 1540s and the attempts of the governments of Henry VIII's children to enforce Dublin Castle / Whitehall control across the island. There were indeed counter-attacks by Irish chieftains on English-led forces, and on each other, but Edwards finds unambigously that the English used violence as a political tool first, and on a larger scale than the Irish were able to (including hitting the common folk as much as the lords).
It's a provocative and counter-revisionist piece, and the editors of the books argue in their introduction (and a number of other contributors agree) that Irish historiography is perhaps more liberated to inquire honestly into the facts of political violence in the past, now that the threat of violence in the present is largely over. One contributor blames C.S. Lewis and W.B. Yeats for whitewashing Spenser, who was clearly initmately involved with the 1580 massacre at Smerwick. On the same period, Hiram Morgan has a typically profound analysis of the murders carried out on the orders (probably) of Hugh O'Neill.
There are a number of pieces on the traumatic 1640s, the best being one by Kenneth Nicholls on the 1642 massacres of Catholics by Protestants in Leinster and Munster (which followed the even bloodier 1641 massacres the other way round in Ulster), though I was also interested to read John R. Young's account of the reception of Protestant refugees from Ulster in Scotland (it's a shame that he doesn't match this up with Ulster geography) and Mark Clinton, Linda Fibiger and Damian Shiels on the archaeology of a massacre at Carrickmines south of Dublin.
John Morrill and Micheál Ó Siochrú take two different looks at Cromwell and Drogheda, Ó Siochrú unpacking the contemporary published accounts of the massacre, Morrill looking at it in the context of Cromwell's whole career - anti-Irish and anti-Catholic, but markedly less so than most of his allies. While Ó Siochrú sticks to (and reinforces) orthodox interpretations, Morrill is interestingly revisonist: for instance, he interprets Cromwell's infamous description of those he ordered killes as "barbarous wretches, who have imbrued their hands with so much innocent blood" as referring to Royalists in general rather than Irish Catholics in general.
Anyway, relatively cheap for an academic volume and worth a read for a deeper understanding of the topic of the title. A couple of the writers make parallels with more recent wars in the Balkans, and I can see the point, though will have to reflect a bit further.