From the Orange Prize-winning author of We Need to Talk About Kevin, Allergic to group activities of any kind, all her life Serenata has run, swum, and cycled -- on her lonesome. But now that she's hit 60, all that physical activity has destroyed her knees. As she contemplates surgery with dread, her previously sedentary husband Remington, recently and ignominiously redundant, chooses this precise moment to discover exercise. Which should be good for his health, right? Yet as he joins the cult of fitness that seems increasingly to consume the whole of the Western world, her once-modest husband burgeons into an unbearable narcissist. Ignoring all his other obligations in the service of extreme sport, he engages a saucy, taunting personal trainer named Bambi, who treats his wife with contempt. When Remington announces his intention to compete in a legendarily gruelling triathlon, MettleMan, Serenata is sure he's going to end up injured or dead. And even if he does survive, their marriage may not.