Most people remember Colleen McCullough as the author of The Thorn Birds, source of the trashy early-’80s TV miniseries. But McCullough’s no Barbara Cartland: The Australian author, who was a research assistant at the Yale School of internal medicine when she wrote her first two books, has a degree in neurophysiology and owns the world’s largest private library on the Roman Republic. Her ninth book, Caesar’s Women, is the fourth in a projected five-part series chronicling the final decades of the Republic. The novel is accessible enough to open with a scene in which teenage Brutus is chided by his mother for having acne, yet erudite enough to include a 55-page glossary, which includes, among other things, the exact dimensions of a toga (FYI: 15 feet wide, 7 feet 6 inches long). At 7 p.m. at Olsson’s, 1200 F St. NW. FREE. (202) 347-3686.