Zero by Charles Seife is really good. It's basically the history of the number zero. I know that sounds kinda lame, but it turned out to really be amazing. Another book by him that I loved was Alpha and Omega. It's about the origins of the universe and some theories on how it will end.

As for some fiction, The Mists of Avalon by Marion Zimmer Bradley was impressive. It's kinda long, but worth it in the end. There are four other books related to it: The Forest House, Lady of Avalon, Ancestors of Avalon and Priestess of Avalon. Mists of Avalon is basically the legend of King Arthur told from the points of view of the women involved. It's a really interesting take on it.
Some other authors I love are Mercedes Lackey and Amy Tan.