Gingerbread Girl

"There are plenty of established facts concerning 26-year-old Annah Billips. She likes sushi and mountains, but hates paper cuts and beer breath. She dates girls and boys, and loves to travel. She may have a missing sister, or she might be insane. Did Annah invent an imaginary sister named Ginger during her parents' ferocious divorce, or did her mad scientist father extract part of her brain and transform it into a living twin?"