Agree with the Sawyer recommendation from MS4M. And if you're into alternate history, Harry Turtledove is well known for that, and S.M. Stirling has some interesting series.
As for non-fiction, I'm a big linguistics buff, and Bill Bryson has a very readable book in "The Mother Tongue: English and how it got that way". Apparently his "A Short History of Nearly Everything" is quite good too, but I have yet to read that one myself...
"A Short History..." is a good book! I had forgotten that one.

