An Abundance of Katherines

An Abundance of Katherines is a Young Adult novel by John Green.

Summary
Colin Singleton, a child prodigy, has dated nineteen girls named Katherine. After being dumped by his girlfriend, Katherine XIX, Colin feels depressed, so his best and only friend, Hassan Harbish, convinces him to go on a road trip to take his mind off the breakup. After reaching a rural Tennessee town called Gutshot, they visit the supposed resting place of Archduke Franz Ferdinand. It is there where they meet Lindsey Lee Wells and her mother Hollis, whose family runs a local textile mill. Hollis allows Colin and Hassan to stay with her family and offers them a summer job interviewing the town's residents and assembling an oral history of Gutshot. Colin begins to like Lindsey, though she has a boyfriend named Colin Lyford (he and Hassan call him TOC, "The Other Colin"). Colin creates a theorem called the "Theorem of Underlying Katherine Predictability". It determines the curve of any relationship based on several factors of the personalities of the two people in a relationship. His theorem eventually works for all but one of his past relationships with a Katherine. Hassan finds a girlfriend, Katrina, a friend of Lindsey's, but they break up when Katrina and TOC hook up, also breaking up Lindsey's relationship. Colin finds Lindsey at her secret hideout in a cave, where he tells her the story of every Katherine he has ever loved. Lindsey tells him how she does not feel sad but instead slightly relieved by TOC's affair. They discuss what it means to them to "matter" and eventually confess their love for each other. As their relationship continues, Colin decides to use his dating formula to determine whether he and Lindsey will last. The graph reveals that they will only last for four more days. Lindsey slips a note under his door, four days later, stating that she cannot be his girlfriend because she is in love with Hassan. But she leaves a P.S. stating that she is joking. Colin realizes that his theorem cannot predict the future of a relationship; it can only shed light on why a relationship failed. Despite this, Colin is content with not "mattering". Hassan says that he is applying for two college classes, which Colin has been trying to convince him to do throughout the book. The story ends with the trio driving past the restaurant they were originally planning to go to, because Colin, Lindsey, and Hassan realize that they can just keep driving; there is nothing stopping them from continuing on.