The Bell Jar is a novel about a young woman, Esther Greenwood, who suffers from a mental illness. It is not clear what specific mental illness she has, but it is clear that she is struggling to cope with her life. She has a history of depression and suicidal thoughts, and she has been hospitalized for her mental health in the past. The novel follows her as she tries to recover from her mental illness and find a new sense of purpose in her life.