Interesting patterns and places I see where I need to explore more. Would have been more interesting if I could have been able to color-code it by male/female writers, but it'll do for a start. If I counted correctly, I've read at least one book from a writer who was born/lived in 86 different nation-states. That's less than half and only a little more than a third of the extant countries today.
Here's another one, featuring the US states and writers from those states that I know I've read at least one author associated with that state.