It was while researching a novel that John Lanchester stumbled on the most interesting story he’d ever found: the perfect storm of events and attitudes that caused today’s Great Recession. I.O.U. is that story. Writing with a novelist’s storytelling flair, Lanchester explains the rules of the “dismal science” of economics, and the disaster that happened when mathematical geniuses created investments that completely ignored the reasons behind those rules. The title of the book refers to the last chapter in which Lanchester looks ahead to the struggle between the public and private sector over how to pay the bill. This is tragic Econ 101 for humanities majors.