Following Jon's edict, I'm going to nominate a non-fiction book that has been on my TBR list for some time. It's probably not everybodies cup of tea, but the story has fascinated me.
Don't Sleep There Are Snakes
From the above article:
The Pirahã Indians of the Amazon are a very peculiar people. They number fewer than 400 and have no myths, rituals or history. Their language is unrelated to any other living tongue. It can be whistled, sung, hummed or spoken. It has no words for numbers, colours, left or right, brother or sister.
Nearly everything we know about the Pirahã comes from Daniel Everett. He first visited them as a missionary in 1977 with the intention of learning enough of their language to translate the New Testament; 30 years later he is no longer a Christian, let alone a missionary, but chair of languages, literatures and cultures at Illinois State University, and something of a celebrity on the international lecture circuit.