My World Turned Upside Down

I've been reading (and will finish soon!) a recent collection from Baen Books called The World Turned Upside Down. It's a collection of short stories that had a deep impact on the authors (Eric Flint, David Drake and the late Jim Baen).

What short works of fiction or non-fiction have turned my viewpoint "upside down"?

H. Beam Piper: Omnilingual. This story is part of one of Piper's extended series, the Terro-Human Future History. For a long time I was not aware of other works by Piper, and especially not aware that there was a series. Imagine my cries of joy when Ace Books came out with a trade paperback called Federation and discovered that not only was it a series, but Ace was re-publishing them.

An expedition to Mars discovers the remains of a human-like civilization. In exploring the ruins, they come across a treasure trove, a library that is mostly intact. But how to read the books when there is no common link between the cultures of Earth and the cultures of Mars? Years before I started reading Carl Sagan, Piper introduced me to a Rosetta Stone for galactic societies. Toss in some characters that you don't normally encounter in a science fiction story (linguists, archaeologists) and a classic setting (Mars) and you've got a wonderful story.