How the Irish Saved Civilization: the untold story of Ireland's heroic role from the fall of Rome to the rise of medieval Europe.
by Thomas Cahill

This book was mislabeled. Some possible title might be:
Random thoughts about the Irish that I was not able to publish anywhere else
Blogging the Sixth Century

He doesn't get to the title until the very end of the book and the case is not convincing. He basically says that the Irish saved a lot of old books and kept literacy alive for about 300 years from about 400 to 700. He does not make a strong case for this. Certainly the Irish did some good things but they all would have been done by other people if they had not done them. They did not "save civilization" this is a huge exaggeration.

I checked out the reviews on Amazon, lots of 4 and 5 stars and lots of 1 and 2 stars. It seems you either loved it or hated it. There was general agreement that the history was weak.