Ferriter, Diarmaid. A Nation and Not a Rabble: The Irish Revolution 1913-1923. New York: Harry N. Abrams, 2017. 528 pages, paperback.

This is not, directly, a history of the Troubles of the 60s-90s. But, it has a great final section (5 chapters I believe) on the memory and legacy of the Revolution in various groups, including belligerents in the Troubles. It's really good social/cultural military history, and I think you can't understand the Troubles without understanding the complex intersection of memory and politics for different groups.