Angela's Ashes, not nonfiction perse but memoirs of the author's life as a child/teen/YA in Ireland

One Man's Terrorist by Daniel Finn was an extremely interesting, but dense history of the IRA. It may be too specific for what you're searching for, but I couldn't help but to recommend it.

I read Ireland and the British Empire ed. Kevin Kenny to gain perspective on Spenser's detestable views. It was definitely interesting, but the quality of writing wasn't great throughout.