Why do you think the author has ended the book close to where it began?

This is called framing the story. This allows Steinbeck to ultimately emphasize how much has changed since the novel's opening. Where George was once full of life - angry and forgiving - now he is a husk of himself, bereft of emotion as he goes through his monologues. What was once a plausible - if far-fetched - fantasy has disintegrated into delusion.