It might be impossible to wrest the mass of contradictions and battling factions that is Catholicism into a single volume. Indeed, when I told my wife what I was reading I noted that it only stretched from The French Revolution, so "barely scratching the surface." But, all smartass quips aside McGreevy probably comes as close as humanly possible.
The genius of his history is to show that the battle lines that modern Catholics take as fixed and for granted are actually ever shifting and nebulous. The text introduces the Jesuits, now understood as the intellectual "liberal" wing of the church as a gleeful orthodoxy enforcing goon squad. Surviving a staking in the coffin that was the banishment of their order to rise to new levels of power and drive the liberal wing of reformers into powerless ignominy. Meanwhile the conservative wing approvingly reads Marx and longs for the days when pesky Capitalism will fall to ruin.
McGreevy does not let the fact that he's telling the story of a movement keep him from highlighting the individuals who make up the church. A never ending cavalcade of lunatics, perverts, reformers, genius level politicians, fools, revolutionaries, lickspittles, artists, prudes and occasional saints who have made up the church into an infuriatingly improbable singular whole. It is a brilliant example of function following form. After all, we are told the church is a superstructure in time, a collective whole made up of people who probably wouldn't speak to one another at a party. For such a dense work, Catholicism is readable, and McGreevy deploys a dry wit and a taste for particularly bitchy pieces of court pageantry and intrigue that never make the book less than entertaining.
Is the church a regressive force that has kept many suffering? Or a dependable bulwark of human dignity? Is it a foot dragging, conservative force that refuses to reckon with itself, or does its stubborn inertia, lack of care of trends and unshakeable belief in the value of every single human life, allow it to stand dependably against evils from Eugenics to genocide. Is it the tool of colonizers and racists or a dependable source of indigenous empowerment with its generations of indigenous clergy? Is it the natural ally of dictators, or a force that brings them down with stunning regularity. The answer is of course, yes.
To anyone who has dedicated themselves at any level to this institution and often finds themselves wondering if it was truly for the good as they stare down a coming generation of Harrison Buckners, McGreevy's book delivers the comforting message, "Don't worry, you don't know how this will turn out." This is after all the message Catholicism delivers as well.
Postscript: One small criticism of McGreevy's work is that it surprisingly withholds a verdict on the most controverisal Pope of the 20th century (really saying something) Pius XII, the so called "Hitler's Pope". Whether Pius can fairly be labeled a supporter of Hitler, or if he was simply engaged in real politick to minimize as much harm as he could is one of the essential questions of 20th century Catholicism. You will certainly find a mountain of books to support either reading.
Perhaps McGreevy simply considered this a settled issue and thus didn't want to spend a large chunk of his page count on it (the complicity or lack there of, of workaday German Catholic civilians in Nazi Germany is extensively covered). But for the lay reader who presumably isn't going to reach for another Catholic tome after finishing this one, it is a strange omission. For example Diarmaid Macculloch's excellent history of Christianity spent more time considering the question despite the fact that it only regarded Catholicism as a sect among many. It just comes as a strange omission.