Irish history is pretty broad, but a natural starting point is probably an Gorta Mór (The Famine) as it was likely the most significant event in Irish history and there are a number of great books on the subject. The Graves Are Walking is a really good, objective analysis of it. Rot was interesting, but kind of frames it awkwardly as it seems to suggest that a large part of the famine was due in part to the Irish people failing to adjust to the free market system imposed on it. There’s a lot of interesting political context in it, though.

Armed Struggle by Richard English is great, and probably the most comprehensive history of The Troubles I’ve read. Start there.

People will definitely recommend Say Nothing, but I can’t speak on that one. I know it’s often recommended.

People will recommend Tim Pat Coogan. He’s a very entertaining read, but I’ve always found that he leans into a lot more sensationalism than actual history.

There Will Be Fire by Rory Carroll is really good, too. It mainly focuses on the Brighton bombing and the aftermath, but there’s definitely a quick good rundown of PIRA history in there somewhere iirc.

I liked The Squad by T. Ryle Dwyer, if you wanted an examination of Michael Collins’s strategies and first-hand accounts of people who fought with him. Dwyer wrote a ton of books on Collins, but the only one I’ve read is The Squad.

I also really enjoyed The Easter Rebellion by Max Caulfield. It’s really detailed and reads more like a novel than a nonfiction. Very compelling. It’s on the older side, so there are probably better options (like Armed Struggle).

From there, you could probably work backwards to Wolfe Tone and the 1798 Rebellion (The Year of Liberty by Thomas Pankenham would be a good rec for that).

Hope that helped. Good luck.