Gregory Maguire - he's written three books I know of, Wicked, Confessions of an Ugly Stepsister, and Mirror, Mirror - -He takes stories we know so well (the wizard of oz, CInderalla, and Snow White) and tells the story of the "villian". The wicked witch was definitely misunderstood
Margaret George - A bunch of historical biography types (One on Cleopatra was fascinating, Mary, Called Magdelene I think was partly fiction but didn't read like it, and she's also got one on Henry VIII.
Jeff and/or Michael Shaara - I am partial to For Love of the Game because I love the movie, but there are abunch of Civil War books Gods and Generals (movie of the same name), The Killer Angels (Gettysburg was based on this book if I remember correctly) there are a few other books in the Civil War series. There's also an American Revolution series that's currently sitting on my nightstand.
Armistead Maupin - has a series of books, Tales of the City (PBS did them as a series about a decade ago, and it was wonderfully done) the books were about the residents of an apartment complex in San Francisco in the 70s -- the books were fantastic...