Anything by David Weber. His books are in the sci-fi section. I haven't read his Armageddon Reef series, but I've read everything else he's written. His Honor Harrington and Dahak series are excellent, while his Path of the Fury stand-alone (and its expansion, In Fury Born) are perhaps the most exciting science fiction books I've ever read.
Elizabeth Moon is a wonderful author. Read her Vatta's War and Serrano series, as well as her stand-alone Remnant Population.
Military science fiction (David Drake) and time-travel stories (Eric Flint) are good, and classic science fiction (Heinlein, Asimov, etc.) are always good. And Orson Scott Card is always good (Tales of Alvin Maker, Ender's Game, etc.), if a bit formulaic in his later years (e.g., Empire).
Do you like British humor? Try Good Omens.
Historical romance? Jennifer Wilde, Julia Quinn, Carla Kelly, Jude Devereaux, Beatrice Small, or Johanna Lindsey are good for historical detail in their stories.
Westerns? Zane Gray or Louis L'Amour, hands down.
Southern Gothic? Pat Conroy, hands down.
Children's books? Anything by Elizabeth Enright, Laura Ingalls Wilder, Robert Lawson, E. B. White, or Robert McCloskey is good.
Books from the golden age of American literature? Anything by Edna Ferber, hands down. Also Louisa May Alcott, interestingly enough.
NCbear (who's also hastily scribbling down authors and titles to go find in rapidly emptying Borders stores)