Idiopathy by Sam Byers

Idiopathy - HBFourth Estate

Katherine has given up trying to be happy. 30 years old, stuck in a town and a job she hates, her mounting cynicism and vicious wit repel the people she wants to attract, and attract the people she knows she should repel. When Katherine and Daniel, her ex, find that their former friend Nathan has returned from a stint in a psychiatric ward, they decide to meet to heal old wounds and reaffirm their friendship. But will a reunion end well?