Birdie and Cole Lee are sisters so close, they live in their own private world and speak to each other in Elemeno, their secret language. As they grow up in ’70s Boston, their father sees them as an experiment. Biracial people, he theorizes, are “canaries in the coal mine” determining the toxicity of society’s racial atmosphere. His children are the first generation to breathe that poisoned air and make it through—”a little injured, perhaps, but alive.” Their parents’ marriage collapses; soon after, fear of government retaliation for revolutionary activities forces the family underground. Their mother takes Birdie, who can pass for white, while their father departs with the darker Cole and his new girlfriend to Brazil. Caucasia, Danzy Senna’s first novel, follows Birdie’s wanderings through the mazes of identity, race, and adolescence, searching for the parts of herself that were lost and denied when her family split up. Senna reads from and signs copies of Caucasia at 7 p.m. at Olsson’s Books & Records, 1200 F St. NW. Free. (202) 347-3686. (Dawn L. Hannaham)