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Guns, Germs, and Steel by Jared Diamond is one of my favorite non-fiction books.
The science is geared towards the layperson and once you get past him being impressed with himself it's a great read.
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Good thing I checked replies before responding with this.
Another one is
Godel, Escher, Bach: An Eternal Golden Braid which is a truly excellent book on incompleteness theory, self reference and artificial intelligence (from a theoretical perspective). Very math oriented but also has a lot of good stuff for non-math people, just a truly excellent book all around.