"You forget that the world is full of ordinary decent people like yourselves, good Samaritans who'll stop and help a soul in need. " Many books have been written about various mental health conditions from depression to Alzheimer. However, not much has been written about the epidemic of the current age that is acute loneliness. Every individual is expected to be having a bustling social life apart from their home and work routine.   

Eleanor, the main character of the story, is easily identifiable. Majority of the workplaces have an Eleanor. The person who appears to be looking at every situation as an outsider, who seldom speaks about things other than the present situation and whose personal life is not much known to the world. The protagonist's life is streamlined, scheduled and rather vacant.
Various reasons have led to her isolation. The reasons are revealed as the story progresses; explaining if it is anything amiss in her personality or if the ability to navigate and show acceptable social behaviour depletes, as a person retreats from regular social interaction.
Nevertheless, the story culminates with a happy ending for Eleanor with the final takeaway of the book that it is never too late for anyone. 

-Honeyman, Gail. Eleanor Oliphant is Completely Fine (New York : Pamela Dorman Books, 2017)