LONDON -- Books about a Haitian revolutionary, The Beatles and the brain are finalists for Britain’s leading nonfiction literary award.Contenders announced Thursday for the 50,000-pound ($65,000) Baillie Gifford Prize include Sudhir Hazareesingh’s “Black Spartacus,” a biography of Toussaint Louverture, who led a slave uprising that sparked Haitian independence in the 18th century; Craig Brown’s “One Two Three Four: The Beatles in Time” and Matthew Cobb’s “The Idea of the Brain."Also on the