This was the first of my father's four books, published in 1958 when he was 30, as adapted from a postgraduate thesis. It tells the story of the short-lived group of MPs for Ireland in the 1850s campaigning for increased rights for agricultural tenants and equal rights for Catholics. It's an interesting study of a relatively minor piece of history. I understand there's been precisely one other book published on the subject in the last fifty years...
The "Independent Opposition" won almost half of the Irish seats in the 1852 general election, largely because of two gratuitously anti-Catholic moves by British politicians in the months before the vote - the outgoing Whig government of Lord John Russell passed the Ecclesiastical Titles Bill, and then Lord Derby's caretaker Tory government made a proclamation that sparked anti-Catholic rioting in Stockport immediately before the election. It's extraordinary that the Famine per se, only recently past, doesn't seem to have been a political factor that played in 1852 (the first election since 1847). The death of O'Connell in 1847 and the dismal failure of the 1848 rebellion seem to have been bigger factors, though if anything they militated against the consolidation of any nationalist movement. (And despite some wishful thinking and a very few exceptions this movement does seem to have been pretty much restricted to Munster, Leinster and Connacht.)
It failed, in my father's analysis, mainly because of a lack of leadership. Two of its most interesting characters, John Sadleir and William Keogh, defected to the new Liberal government almost as soon as the votes had been counted. Any one of several other potential leaders could have built it into a more long-lasting movement, but one by one they fell by the wayside - Frederick Lucas (the founder of The Tablet) died suddenly at the age of 43, George Henry Moore was kicked out of parliament for electoral malpractice, and Charles Gavan Duffy gave up in despair and emigrated to Australia (where he became Prime Minister of Victoria). The odds were stacked against any party whose policy was concerted opposition rather than the personal advancement of its own members, and the failure of the 1850s movement makes the success of Parnell a generation later all the more remarkable.
Edited to add See post on Trollope.