I was a " 'tween," I think --
on the cusp of teenagerhood, someplace
(it's a marketing category nowadays, from merchandise to TV shows) --

when I picked up one day
a hardcover anthology of short stories from soup to nuts,
all genres within the format, all kinds of authors.

I was entirely unprepared for
"The Machine Stops" by E. M. Forster,
positively science fiction.
It stopped me in my tracks.
I've never forgotten it.