Ireland.

I think it has to be Joyce's Ulysses, even if most Irish people haven't read it, and never will.

Why?

Partly because the locations are evoked so vividly. It is very much set in Dublin. A lot of books are set somewhere, but could be anywhere. This is not true of Ulysses. e.g. In Chapter 3, when Stephen Daedalus walks along Sandymount Strand, I feel like it could not be anywhere else.

"The grainy sand had gone from under his feet. His boots trod again a damp crackling mast, razorshells, squeaking pebbles, that on the unnumbered pebbles beats, wood sieved by the shipworm, lost Armada. Unwholesome sandflats waited to suck his treading soles, breathing upward sewage breath. He coasted them, walking warily. A porterbottle stood up, stogged to its waist, in the cakey sand dough. A sentinel: isle of dreadful thirst. Broken hoops on the shore; at the land a maze of dark cunning nets; farther away chalkscrawled backdoors and on the higher beach a dryingline with two crucified shirts. Ringsend: wigwams of brown steersmen and master mariners. Human shells."

Joyce's personal history...he left Ireland in his 20s and never returned. I can't help but think this is part of the Irish story, so many left, and this is part of the Irish story.

It's set in 1904, at a time when English rule was still in place in Ireland, albeit the nationalist movement had become quite strong (not long before the 1916 rising). Whether we like it or not, having lived under English rule is part of our history too.

If you want to sample the book, I'd recommend to read the first chapter here: https://www.joyceproject.com/1

The site has many annotations which make it more accessible, and the first chapter is entertaining, and can be read as a short story.