Bill Bryson, "A Short History of Nearly Everything"
Written by a travel writer, who's pretty witty...
Bill gets tired of being around science types, so he wrote an idiot's guy to science. Starts with the big bang, formation of planets, string theory, geology, biology, etc moves to genetics. Specifically he uses common means to explain complicated topics once meeting with the scientific illuminati.
For instance, on the vastness of space - if the earth was the same size as the period at the end of this sentence, if you were to keep the scale the same, you'd need sheets of paper 1 1/2 miles long to include pluto in the solar system. He also discusses the scientists' quirks in figuring out their theories to start with (for instance - one guy would subject his wife and kids to vacuums, where they would pass out and then go eat dinner).
http://www.randomhouse.com/features/bil … 0767908184